[clang] Fix enum enumerator visibility loss when #include is between module imports (PR #188865)

[Michał Chojnowski via cfe-commits]

michoecho wrote:

> Clang 22.1.1 (unpatched) also does not reject the redefinition. The patch does not cause a regression, and it is yet another bug.

@avikivity Are you sure? I didn't check that specific version, but both 22.1.0 and trunk reject it: https://godbolt.org/z/5T14chvz4

https://github.com/llvm/llvm-project/pull/188865