[clang] Fix build failure in CommonArgs.cpp on MSVC 2022: warning C4715: 'clang::driver::tools::complexRangeKindToStr': not all control paths return a value (PR #159408)

[Shunsuke Watanabe via cfe-commits]

https://github.com/s-watanabe314 approved this pull request.

Looks good to me. However, `llvm_unreachable` seems to have already been merged in #159330. Removing the `break` is fine.

https://github.com/llvm/llvm-project/pull/159408