[About W3C WAI] update based on June 2024 tweaks for Ford proposal

[shawna-slh]

page: https://www.w3.org/WAI/about/

edits:

• Ensure that W3C specifications support accessibility.
  -> Ensure that all W3C specifications support accessibility.

...

(fyi @iadawn here's a placeholder to add things after we agree. (keeping in mind this page may be a tad different from the proposal.))