[clang] [Clang] Deleting an incomplete enum type is not an error (PR #118455)

[Alexander Kornienko via cfe-commits]

alexfh wrote:

The original file is huge and template heavy, so reduction will take some time. I wonder if you can spot something obviously wrong in the commit given the information above? Failing that, can we revert in the meantime?

https://github.com/llvm/llvm-project/pull/118455