Unignore cloud event notification test

We ignored testCloudEventNotification because it was flaky and unclear
why. The reason was because some of the test utils expect to find at
least a media item in the Picker UI and this particular test typically
had an empty UI on it's first assertion on cuttlefish.

Fixed by creating a placeholder local item to ensure the UI is not
empty

Test: atest CloudPhotoPickerTest
Bug: 215187981
Change-Id: I5908156cbabe2bfaa95315a773c2703cdeb33e67
1 file changed