RingtoneManager#setActualDefaultRingtone() open OutputStream of cacheUri with "wt" mode

the default mode is "w",if the cache file is not deleted successfully before openOutputStream and the size of new ringtone is smaller than old rongtone,the cache file will be a mixture of old and new ringtone.

Bug: 263074833

Change-Id: Ib7a0bf5e2a9f695aa4701c91c0b79c6bce2d76f1