libomp: xgboost incorrect LC_RPATH referenced in libxgboost.dylib

Upon installing xgboost (2.1.2) with pip on macOS (15.0.1) I noticed that there was an error related to not finding `libomp` once installed. In the installed `libxgboost.dylib` the rcpath references an absolute 'homebrew' directory (I don't use homebrew).

% otool -l /opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/xgboost/lib/libxgboost.dylib
```
Load command 15
cmd LC_RPATH
cmdsize 48
path /opt/homebrew/opt/libomp/lib (offset 12)
```
It should likely be changed to use: `@rpath/libomp` unless you expect anyone who doesn't use homebrew to fix the hardcoded path anytime they install xgboost with pip.