TEST_MAPPING: re-enable fixed scheduler test

Turning up
VibratorCallbackSchedulerTest#TestScheduleMultipleCallbacksRunsInDelayOrder
as it has been fixed and passing in post-submit runs.

Test: atest VibratorCallbackSchedulerTest
Bug: 293623689
Change-Id: I33aa73927a5b64fdf7de2e1a8ed897bd278c3ba4
Signed-off-by: Lucas Henneman <henneman@google.com>