Removed an old comment.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178709 91177308-0d34-0410-b5e6-96231b3b80d8
Refactored out a part of ObjCARCOpt::OptimizeReturns into its own method HasSafePathToPredecessorCall.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178710 91177308-0d34-0410-b5e6-96231b3b80d8