Leadership page a11y fixed (Fixes #15335)

[alexgibson]

One-line summary

• Fixes some minor a11y issues on the /leadership page.
• Also removed the sub navigation from this page since it's empty and serves no purpose.

Note I filed a separate issue in Protocol for the incorrect aria role on the side menu: mozilla/protocol#999

Issue / Bugzilla link

#15335

Testing

http://localhost:8000/en-US/about/leadership/

[stephaniehobson]

How do we get the wagtail database to test this locally?

[alexgibson]

@stephaniehobson https://bedrock.readthedocs.io/en/latest/cms.html#fetching-the-latest-cms-data-for-local-work

You should only need the dev DB to test the PR I think (only the prod db has the full leadership data).

[stephaniehobson]

Errors listed in #15335 to be fixed:

• Elements must only use supported ARIA attribute
  • I assume the sidebar is going to be addressed in a separate issue and it's okay to mark [a11y] Leadership page accessibility improvements #15335 as fixed?
• ARIA attributes must conform to valid names
• Heading levels should only increase by one
  • The sidemenu changes are an improvement 👍
  • There is still a problem with the heading levels (even though the test will now pass)
• Page should contain a level-one heading

---

Currently the heading levels for this page make a tree like:

2 Mozilla Corporation
2 Executive Steering Committee
2 Senior Leadership
2 Mozilla Foundation
2 Boards of Directors
2 Mozilla Corporation
2 Mozilla Foundation
2 Former Board Members

I think the correct hierarchy would be:

2 Mozilla Corporation
  3 Executive Steering Committee
  3 Senior Leadership
2 Mozilla Foundation
2 Boards of Directors
  3 Mozilla Corporation
  3 Mozilla Foundation
  3 Former Board Members

Note that the heading level of all the bios will need to be adjusted too.

---

Assuming the sidebar error will be fixed in a separate PR this can merge after some more heading level tweaks.

Thanks for tackling the boring but necessary code changes for better a11y 🙂

[alexgibson]

@stephaniehobson the side menu has been split out into its own component test in #15462, and needs to be fixed upstream in protocol.

Good catch on the heading levels - will update those here 👍

[alexgibson]

@stephaniehobson updated, thanks again

[stephaniehobson]

R+ 🗣️