Remove unnecessary synchronized block

The only two actions within the block are sending an intent and
canceling a job none of which have anything to do with the queuelock

Test: atest -v RunBackupFrameworksServicesRoboTests
Test: atest -v CtsBackupTestCases
Test: atest -v CtsBackupHostTestCases

Bug: 136738613
Change-Id: Ieedb73edf6cd40792232b48a26613b497c87ba02