Disable a flaky test.

This test stays on on V+, as b/286690307 (which is causing the flake)
has been fixed on this branch.

Bug: 286690307
Test: atest SafetyCenterActivityFunctionalTestCases
Relnote: N/A
Change-Id: Ia4e08cc60e34d7e7a999196f99852e2363547530