Remove old ChooserActivity from manifest

The old ChooserActivity should never be triggered and no longer passes
CTS (the intent is already superseded by the IntentResolver version which has a higher priority).

Leave a note for readers that they're likely looking at the wrong
Chooser.

Bug: 282173439
Test: Presubmits
Change-Id: I055cb044ea3bd8f5c645e2a8b7585ac682242d06