docs: Fixing broken Javadoc comments

Two recent checkins broke the Javadoc (in both cases, an <h3> wasn't
properly closed). Made the fix by hand to the HTML output in
cl/309818465 but we need to make the corresponding change to
the Java source or it'll get reverted next time we update the reference
docs.

Staged to:

go/dac-stage/reference/android/content/pm/LauncherApps.PinItemRequest
go/dac-stage/reference/android/service/autofill/AutofillService

go/dac-stage/reference/kotlin/android/content/pm/LauncherApps.PinItemRequest
go/dac-stage/reference/kotlin/android/service/autofill/AutofillService

BUG: 155669442
Exempt-from-owner-approval: Docs-only change
Test: make ds-docs
Change-Id: I97be9550689544304dff276cf3c9406f9cd98408