Missing openmpi_external and mpich_external packages in recent repodata

### Solution to issue cannot be found in the documentation. - [x] I checked the documentation. ### Issue It appears that the openmpi_external and mpich_external packages are no longer resolvable via conda install or conda search on the conda-forge channel. These packages are critical for users needing to link against system-provided MPI implementations (e.g., on HPC clusters) rather than the conda-packaged binaries. ### Installed packages ```shell - ``` ### Environment info ```shell - ```