Remove manually moving a11y focus to app chip on menu close

We manually call for a11y focus on app menu menu close, as a fix to a
previous bug (b/329199667), but this is causing another bug where the
a11y focus jumps to the app chip when opening an app in a browser
window, due to the menu closing. It was already agreed in
b/329195839#comment14, that the app menu is non-modal, therefore there
isn't a requirement that focus must go to this dialog upon opening, so
it should be fine to let a11y focus be determined by talkback  when the dialog
closes.

Bug: 398143241
Test: manually testing
Flag: EXEMPT bugfix
Change-Id: Id65f2b9fc207e67954f302b24219769a34efcd9b