Unlink listener death recipient on alarms

Stopped using BinderDeathDispatcher as deduping is no longer required.
If an app sets the same listener, it is first removed internally which
will result in a call to unlink before the subsequent call to set.

Test: Manually using a test app that cancels and sets an alarm with a
new listener instance in a loop.
atest CtsAlarmManagerTestCases:BasicApiTests

Bug: 189091551
Change-Id: I390d9bba37a4040b7e789e0ae04f9980fbed5c12