…mestamp (#5536)

<!-- READ ME FIRST: Please fill in the explanation section below and
check off every point from the Essential Checklist! -->
## Explanation
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- Explain what your PR does. If this PR fixes an existing bug, please
include
- "Fixes #bugnum:" in the explanation so that GitHub can auto-close the
issue
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Fixes #3842 

This PR removes the `ensureTimestampIsInMilliseconds` function from
`TextViewBindingAdapters`, eliminating the need for the
second-to-millisecond conversion check for greeting timestamps.

### Sreenshots
|Before|After|
|--|--|
|![WhatsApp Image 2024-09-17 at 11 36 52
AM](https://github.com/user-attachments/assets/0978ffe5-9457-4071-8828-a2791e7e4664)|![WhatsApp
Image 2024-09-17 at 11 39 41
AM](https://github.com/user-attachments/assets/5c41cdc1-5287-4979-8969-4057362434c9)|
## Essential Checklist
<!-- Please tick the relevant boxes by putting an "x" in them. -->
- [x] The PR title and explanation each start with "Fix #bugnum: " (If
this PR fixes part of an issue, prefix the title with "Fix part of
#bugnum: ...".)
- [x] Any changes to
[scripts/assets](https://github.com/oppia/oppia-android/tree/develop/scripts/assets)
files have their rationale included in the PR explanation.
- [x] The PR follows the [style
guide](https://github.com/oppia/oppia-android/wiki/Coding-style-guide).
- [x] The PR does not contain any unnecessary code changes from Android
Studio
([reference](https://github.com/oppia/oppia-android/wiki/Guidance-on-submitting-a-PR#undo-unnecessary-changes)).
- [x] The PR is made from a branch that's **not** called "develop" and
is up-to-date with "develop".
- [x] The PR is **assigned** to the appropriate reviewers
([reference](https://github.com/oppia/oppia-android/wiki/Guidance-on-submitting-a-PR#clarification-regarding-assignees-and-reviewers-section)).

## For UI-specific PRs only
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If your PR includes UI-related changes, then:
- Add screenshots for portrait/landscape for both a tablet & phone of
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- For the screenshots above, include both English and pseudo-localized
(RTL) screenshots (see [RTL
guide](https://github.com/oppia/oppia-android/wiki/RTL-Guidelines))
- Add a video showing the full UX flow with a screen reader enabled (see
[accessibility
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- For PRs introducing new UI elements or color changes, both light and
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<!-- READ ME FIRST: Please fill in the explanation section below and
check off every point from the Essential Checklist! -->

## Explanation
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- Explain what your PR does. If this PR fixes an existing bug, please
include
- "Fixes #bugnum:" in the explanation so that GitHub can auto-close the
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  - when this PR is merged.
  -->
Fixes part of #5404 

This PR migrates deprecated `onBackPressed` usage to
`OnBackPressedDispatcher` callback in the following activities and
presenters.

- AdministratorControlsActivity
- AppVersionActivity
- ProfileAndDeviceIdActivity
- MarkChaptersCompletedActivity
- MarkStoriesCompletedActivity
- MarkTopicsCompletedActivity
- ReadingTextSizeActivityPresenter
- ExplorationActivityPresenter
- ResumeLessonActivityPresenter


## Essential Checklist
<!-- Please tick the relevant boxes by putting an "x" in them. -->
- [x] The PR title and explanation each start with "Fix #bugnum: " (If
this PR fixes part of an issue, prefix the title with "Fix part of
#bugnum: ...".)
- [x] Any changes to
[scripts/assets](https://github.com/oppia/oppia-android/tree/develop/scripts/assets)
files have their rationale included in the PR explanation.
- [x] The PR follows the [style
guide](https://github.com/oppia/oppia-android/wiki/Coding-style-guide).
- [x] The PR does not contain any unnecessary code changes from Android
Studio
([reference](https://github.com/oppia/oppia-android/wiki/Guidance-on-submitting-a-PR#undo-unnecessary-changes)).
- [x] The PR is made from a branch that's **not** called "develop" and
is up-to-date with "develop".
- [x] The PR is **assigned** to the appropriate reviewers
([reference](https://github.com/oppia/oppia-android/wiki/Guidance-on-submitting-a-PR#clarification-regarding-assignees-and-reviewers-section)).

## For UI-specific PRs only
<!-- Delete these section if this PR does not include UI-related
changes. -->
If your PR includes UI-related changes, then:
- Add screenshots for portrait/landscape for both a tablet & phone of
the before & after UI changes
- For the screenshots above, include both English and pseudo-localized
(RTL) screenshots (see [RTL
guide](https://github.com/oppia/oppia-android/wiki/RTL-Guidelines))
- Add a video showing the full UX flow with a screen reader enabled (see
[accessibility
guide](https://github.com/oppia/oppia-android/wiki/Accessibility-A11y-Guide))
- For PRs introducing new UI elements or color changes, both light and
dark mode screenshots must be included
- Add a screenshot demonstrating that you ran affected Espresso tests
locally & that they're passing

---------

Co-authored-by: Adhiambo Peres <[email protected]>