Fix UiTranslationManager ErrorProne error.

"Must store Binder.clearCallingIdentity() token as final variable.."

Restoring identity isn't really needed here, but it's better to have to
be defensive -- in case we do add something later for which the calling
identity needs to be restored.

Bug: 177500482
Bug: 182896753
Test: mmma frameworks/base/ RUN_ERROR_PRONE=true
Change-Id: I72acc40f8776d46b3f875cde1759fe03a25e222b