Move Intel CI tests from ubuntu-latest to ubuntu-20.04

[JessicaMeixner-NOAA]

Pull Request Summary

There have been some CI issues with intel. Moving from unbuntu-latest to ubuntu-20.04 resolves this issue.

Description

Updated CI testing from intel from ubuntu-latest to ubuntu-20.04 . This is a temporary fix and issue #910 will remain open until a solution with ubuntu-latest can be found. Thank you to @MatthewMasarik-NOAA who's idea it was to try this and @AlexanderRichert-NOAA who tested this and confirmed this worked with other codes.

Issue(s) addressed

Isssue #910 will remain open, this temporarily fixes this.

Commit Message

Move Intel CI tests from ubuntu-latest to ubuntu-20.04 co-author: Matthew Masarik

Check list

• [x ] Branch is up to date with the authoritative repository (NOAA-EMC) develop branch.
• [ x] Checked the checklist for a developer submitting to develop.
• If a version number update is required, checked the updating version number checklist.
• If a new feature was added, a regression test for testing the new feature is added.

Testing

• How were these changes tested? Through ci
• Are the changes covered by regression tests? (If not, why? Do new tests need to be added?). This is just updating the CI, so no impact to other regression tests.
• Have the matrix regression tests been run (if yes, please note HPC and compiler)? No.
• Please indicate the expected changes in the regression test output, (Note the list of known non-identical tests.)
• Please provide the summary output of matrix.comp (matrix.Diff.txt, matrixCompFull.txt and matrixCompSummary.txt): Was not ran, "passsing" is if the ci runs.

[MatthewMasarik-NOAA]

Thanks @JessicaMeixner-NOAA for your quick response to this issue. I'll approve and merge as soon as the CI completes successfully.

[MatthewMasarik-NOAA]

This PR updates the cache key and sets the ci platform to ubuntu-20.04 from ubuntu-latest, to avoid current build errors.