MM-53813: Fix(accessibility): on channels page (#24122)

* fix(accessibility): on channels page

* fix lint and update dynamic-virtualized-list

* fix snapshot and update per feedback

* fix e2e tests

* fix test

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

webapp/channels/src/plugins/test/__snapshots__/post_type.test.jsx.snap

@@ -71,7 +71,6 @@ exports[`plugins/PostMessageView should match snapshot with no extended post typ
   text="this is some text"
 >
   <div
-    aria-readonly="true"
     className="post-message__text"
     dir="auto"
     id="postMessageText_post_id"