[clang] [CIR] Fix LLVM lowering crashes after #155244 (PR #157471)

[Morris Hafner via cfe-commits]

mmha wrote:

My understanding is that we are not supposed to erase an op that was replaced anymore. `eraseOp` calls `replaceOp` internally which lead to the double replacement assertion failure.

I also think in our case it doesn't really matter whether we use `replaceOp` and `replaceAllUseWith`

https://github.com/llvm/llvm-project/pull/157471