Remove redundant/deprecated method.

JobParameters.getReasonName was only used internally and marked as
deprecated in favor of getReasonCodeDescription. There wasn't a clear
reason for having both methods, so this removes the deprecated method
and changes the users to use the recommended method.

Bug: 141645789
Test: Check output of `adb shell dumpsys jobscheduler`
Change-Id: I09923ef38e29476d48700fd04ad9cfae29b39878