[llvm] [SystemZ] Add SystemZ path for the PR labeler (PR #82515)

[Kai Nacke via llvm-commits]

redstar wrote:

> Am I right that `**/SystemZ/**` is not supported by the labeler so that all paths have to be enumerated?

The documentation for the labeler refers to the minimatch module, and the [doc](https://github.com/isaacs/minimatch?tab=readme-ov-file#comparisons-to-other-fnmatchglob-implementations) there states:

> The double-star character ** is supported by default, (...)

So it should work.


https://github.com/llvm/llvm-project/pull/82515