Enable caption in shell by default

Remove two caption insets related unit tests because new captions don't
work so well with the old workaround. Proper fixes are in progress
tracked by b/254128050.

Bug: 266890800
Bug: 165794636
Test: Presubmit tests.
Change-Id: Iaacd092a964d583579cea74bb863cbe85be230d2
3 files changed