Update CI to use Open MPI 5.0.0 for GNU

[mathomp4]

Description

This PR updates the CI to use Open MPI 5.0.0 for GNU runs. This was found needed due to the new MPI_THREAD_MULTIPLE changes now in develop. (Note: I'm not sure why this isn't needed on discover!)

It also updates the version used for the auto-containers.

Related Issue

Motivation and Context

Makes things work!

How Has This Been Tested?

If the CI runs, it works.

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 change)
• Trivial change (affects only documentation or cleanup)

Checklist:

• I have tested this change with a run of GEOSgcm (if non-trivial)
• I have added one of the required labels (0 diff, 0 diff trivial, 0 diff structural, non 0-diff)
• I have updated the CHANGELOG.md accordingly following the style of Keep a Changelog