[Clang][CodeGen][UBSan] Remove redundant `EmitCheckValue` calls. NFCI (#135141)
`EmitCheckValue` is called inside `EmitCheck`:
https://github.com/llvm/llvm-project/blob/b122956390a6877536927c2b073a0b99f8b9704f/clang/lib/CodeGen/CGExpr.cpp#L3739
The outside calls are redundant because
`EmitCheckValue(EmitCheckValue(V))` always returns `EmitCheckValue(V)`.
Required by https://github.com/llvm/llvm-project/pull/135135.