llvm::sort(C.begin(), C.end(), ...) -> llvm::sort(C, ...)

Summary: The convenience wrapper in STLExtras is available since rL342102.

Reviewers: rsmith, #clang, dblaikie

Reviewed By: rsmith, #clang

Subscribers: mgrang, arphaman, kadircet, cfe-commits

Differential Revision: https://reviews.llvm.org/D52576

llvm-svn: 343147