configure: remove workaround for gcc's -Wno-maybe-uninitialized

Since r174770 gcc version check is not needed because CXX_FLAG_CHECK
implements the workaround itself.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175080 91177308-0d34-0410-b5e6-96231b3b80d8