CompatHelper: bump compat for MPI to 0.20, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the MPI package from 0.17.2, 0.18, 0.19 to 0.17.2, 0.18, 0.19, 0.20.
This keeps the compat entries for earlier versions.

Note: I have not tested your package with this new compat entry.
It is your responsibility to make sure that your package tests pass before you merge this pull request.

[coveralls]

Pull Request Test Coverage Report for Build 3179497683

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 65.4%

---

Totals
Change from base Build 3007206871:	0.0%
Covered Lines:	1686
Relevant Lines:	2578

---

💛 - Coveralls

[codecov]

Codecov Report

Base: 73.25% // Head: 73.25% // No change to project coverage 👍

Coverage data is based on head (acb6159) compared to base (ecd08c3).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #99   +/-   ##
=======================================
  Coverage   73.25%   73.25%           
=======================================
  Files          26       26           
  Lines        2004     2004           
=======================================
  Hits         1468     1468           
  Misses        536      536           

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.