Add updateable fields to EXTRA_CHOOSER_ADDITIONAL_CONTENT_URI definition

EXTRA_CHOOSER_RESULT_INTENT_SENDER and EXTRA_METADATA_TEXT weren't
checked in when the initial API was submitted (they're the extras for
other new sharesheet APIs), but they're also updateable via shareousel.

Bug: 324574944
Test: N/A
Change-Id: I6e077b461073be6fe8aa2b84130c2e3f594425e5