[llvm] [mlir] Fix nested codeowners for vector dialect (PR #115473)

[Andrzej Warzyński via llvm-commits]

banach-space wrote:

> Yes, it's in github docs: #118208 I can raise a new pr to add that into the CODEOWNERS summary

Wrong link :)

> My opinion is that we should limit the rules to dialects or well-defined coarser-grained components. Having rules per .h/.cpp file or small subfolders is too fine grained and introduces too much noise in the CODEOWNERS file.

+1 I propose having one rule for `Vector`. For finer-grain control, we could use GitHub sub-scriptions.

https://github.com/llvm/llvm-project/pull/115473