Make sure to clear outdated screenshot of splitting tasks

Make sure to clear the screenshot of splitting tasks if it's taking the
new one or being dismissed from split.

Bug: 272420717
Bug: 278134600
Test: pass existing tests
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:e4ec07516eb1b824e25d57088963984d2175e5d7)
Merged-In: Ia159deccc8f0024143200e4dd44fadf67974a198
Change-Id: Ia159deccc8f0024143200e4dd44fadf67974a198
1 file changed