Revert "Update test activities with a non-default icon."

Revert submission 29570743-fix-default-app-icons

Reason for revert: possible culprit of b/371183869

Reverted changes: /q/submissionid:29570743-fix-default-app-icons

Change-Id: I6be362d03791893f94d3393bf9c9ffc4d9e83ec9