removes mhv button on sign-in modal for staging

[CaitHawk]

Are you removing, renaming or moving a folder in this PR?

• No, I'm not changing any folders (skip to TeamSites and delete the rest of this section)
• Yes, I'm removing, renaming or moving a folder

If the folder you changed contains a manifest.json, search for its entryName in the content-build registry.json (the entryName there will match).

If an entry for this folder exists in content-build and you are:

1. Deleting a folder:

   1. First search vets-website for all instances of the entryName in your manifest.json and remove them in a separate PR. Look particularly for references in src/applications/static-pages/static-pages-entry.js and src/platform/forms/constants.js. If you do not do this, other applications will break!
      • Add the link to your merged vets-website PR here
   2. Then, Delete the application entry in registry.json and merge that PR before this one
      • Add the link to your merged content-build PR here

2. Renaming or moving a folder: Update the entry in the registry.json, but do not merge it until your vets-website changes here are merged. The content-build PR must be merged immediately after your vets-website change is merged in to avoid CI errors with content-build (and Tugboat).

⚠️ TeamSites ⚠️

Examples of a TeamSite: https://va.gov/health and https://benefits.va.gov/benefits/. This scenario is also referred to as the "injected" header and footer. You can reach out in the #sitewide-public-websites Slack channel for questions.

Did you change site-wide styles, platform utilities or other infrastructure?

• No
• Yes, and I used the proxy-rewrite steps to test the injected header scenario

Summary

This PR removes the MHV button on our Sign-In Modal and Sign in page in our staging environment

Related issue(s)

Jira TIcket

Testing done

• Unit tests passing

Screenshots

Before	After

What areas of the site does it impact?

• LoginActions component
• staging.va.gov/sign-in
• staging.va.gov/?next=loginModal

Acceptance criteria

• remove My HealtheVet sign-in button and related content in vets-website staging environment

Quality Assurance & Testing

• I fixed|updated|added unit tests and integration tests for each feature (if applicable).
• No sensitive information (i.e. PII/credentials/internal URLs/etc.) is captured in logging, hardcoded, or specs
• Linting warnings have been addressed
• Documentation has been updated (link to documentation *if necessary)
• Screenshot of the developed feature is added
• Accessibility testing has been performed

Error Handling

• Browser console contains no warnings or errors.
• Events are being sent to the appropriate logging solution
• Feature/bug has a monitor built into Datadog or Grafana (if applicable)

Authentication

• Did you login to a local build and verify all authenticated routes work as expected with a test user