Update inner class constructor refs to use proper syntax.

Previously, we generally required fully qualified names for referring
to inner class constructors (like #Notification.Builder()) despite that
not being valid javadoc. Now, we properly support #Builder() syntax and
the old syntax will error.

Bug: 6963924
Test: make doc-comment-check-docs
Exempt-From-Owner-Approval: cherry-picked from master
Change-Id: Ib2e4360493275b79c72487ee1cb173bb5e0fd35f
Merged-In: Ib2e4360493275b79c72487ee1cb173bb5e0fd35f
(cherry picked from commit 4c4aa412)