Fix test to allow MPI greater than 3

[bhazelton]

Description

Change the MPI version test to check that the MPI version is greater than or equal to 3 rather than exactly 3.

Motivation and Context

Now that MPI 4 is out and is being picked up by CI runs, this is causing errors (e.g. in pyradiosky's external tests).

Types of changes

• [x] 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)
• [ ] Reference simulation update or replacement
• [ ] Documentation change (documentation changes only)
• [ ] Version change
• [ ] Build or continuous integration change

Checklist:

For all pull requests:

• [x] I have read the contribution guide.
• [x] My code follows the code style of this project.

Bug fix checklist:

• [x] My fix includes a new test that breaks as a result of the bug (if possible).
• [x] All new and existing tests pass.
• [ ] I have checked that I reproduce the reference simulations or if there are differences they are explained below (if appropriate). If there are changes that are correct, I will update the reference simulation files after this PR is merged.
• [ ] I have checked (e.g., using the benchmarking tools) that this change does not significantly increase typical runtimes. If it does, I have included a justification in the comments on this PR.
• [ ] I have updated the CHANGELOG.

[codecov[bot]]

Codecov Report

Merging #396 (7742278) into main (8092079) will decrease coverage by 1.22%. The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #396      +/-   ##
==========================================
- Coverage   99.34%   98.11%   -1.23%     
==========================================
  Files          13       13              
  Lines        2126     2126              
==========================================
- Hits         2112     2086      -26     
- Misses         14       40      +26     

Impacted Files	Coverage Δ
pyuvsim/astropy_interface.py	42.85% <0.00%> (-57.15%)	:arrow_down:
pyuvsim/profiling.py	88.63% <0.00%> (-9.10%)	:arrow_down:
pyuvsim/uvsim.py	98.28% <0.00%> (-1.15%)	:arrow_down:
pyuvsim/simsetup.py	98.84% <0.00%> (-1.05%)	:arrow_down:

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