Follow-up: Show RingtonePickerActivity in work user instead

Due to the fact that the activity is now running in the target user,
remove special user handling codes.

Bug: 37197930

Test: Try to import custom ringtone in work profile, no crash observed
      Set the custom one as default is also working.

Change-Id: I994df3163c505abc18725cc36cc33a7e30faa577
1 file changed