Removed flaky annotation from testFocusedWindowMultipleDisplays

No longer flaky

https://dashboards.corp.google.com/google::_550f6bcf_09dd_4963_b94c_d243e37d002f?f=class_name:in:com.android.server.wm.DisplayContentTests&f=test_name:in:com.android.server.wm.DisplayContentTests.testFocusedWindowMultipleDisplays&f=run_date_usec:eq:(null)&f=presubmit:in:false&f=build_id:eq:(null)

Change-Id: I10504a24144e7636ab7205a079415f6d4eeba043
Fixes: 37908381
Test: self