[clang] [Sema] [Modules] Remove unrelated module partitions from suggestion list (PR #187657)

[via cfe-commits]

mikomikotaishi wrote:

Can you be more specific about what you mean by setup?

If you were curious, I have
```
clangd version 22.1.1
clang version 22.1.1
cmake version 4.3.0
Features: linux
Platform: x86_64-pc-linux-gnu
Target: x86_64-pc-linux-gnu
Thread model: posix
```

As for the question of support for module name suggestions after `import`, see clangd/clangd#2622.

https://github.com/llvm/llvm-project/pull/187657