Remove extra subroutine for all_reduce_min_max in mpi utilites

[mjs2369]

Description:

Removed an unnecessary subroutine since all_reduce_min_max and broadcast_minmax were doing the work of a single subroutine.

Fixes issue

fixes #762

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

Documentation changes needed?

• My change requires a change to the documentation.
  • I have updated the documentation accordingly.

Tests

Compiled and ran lorenz

Checklist for merging

• Updated changelog entry
• Documentation updated
• Update conf.py

Checklist for release

• Merge into main
• Create release from the main branch with appropriate tag
• Delete feature-branch

Testing Datasets

• Dataset needed for testing available upon request
• Dataset download instructions included
• No dataset needed

[hkershaw-brown]

Compiled and ran lorenz

lorenz doesn't call broadcast_minmax (or all_reduce_min_max) so this is not a great test for this pull request.
You can use the github action to run all quickbuild.sh: https://github.com/NCAR/DART/actions/workflows/run_all_quickbuilds.yml