[Passwords] Add comment to ManagePasswordsReferrer ...

.. that Android entries need to be handled in the credential manager
launcher.

Change-Id: I3ddfe218d68914f249d74d1c3ae24770c8dd03ea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4003288


Commit-Queue: Ioana Pandele <ioanap@chromium.org>
Reviewed-by: Mohamed Amir Yosef <mamir@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1072214}