Enable testMediaRecommendationDisabled

It simply removes @ignore and replaces the foreground executor with
uiExecutor because it is the one used in removing the recommendation.

Bug: 229838140
Test: atest MediaDataManagerTest.
Test: checked via forrest/atest to make sure it is not flaky.
Change-Id: I758a950a061c6bb20b9cc6a5484500a8609078a6