Fix javadoc for Context.TETHERING_SERVICE

Users of the API receive a TetheringManager from getSystemService; they
do not call ServiceManager.getService.

Bug: 151243982
Test: m
(clean cherry-pick from internal branch)
Merged-In: If75f590da17f07ea9d65635065689d8f4e17b40f

Change-Id: I129ffa7abae1218bcf88ccb8ba074ec8ad50119b
1 file changed