TEST_MAPPING: remove bug tag and leave module in postsubmit

Even after fixing the tests, AccessibilityMenuServiceTests is still
slightly too flaky to run in presubmit. The module owners are fine
leaving the module in postsubmit.

Bug: 324945360
Test: git diff
Flag: TEST_ONLY
Change-Id: If924aeb2a4d92bba3cc94c5fc8a9e00a3e1743c0
Signed-off-by: Lucas Henneman <henneman@google.com>