Unhide constant AmbientContextEvent.EVENT_BACK_DOUBLE_TAP.

Test: local build mma
Test: "atest CtsAmbientContextServiceTestCases",
Test: "atest FrameworksServicesTests:AmbientContextManagerServiceTest"
BUG: 242480433
Change-Id: I0c73ad5d416523cdb90300c8aa00ad22f901342d
2 files changed