(test) Don't run Mend on fork

[sjberman]

Problem: Mend workflow was running on forks, which would fail since proper secrets aren't set.

Solution: Don't run on forks.

Proposed changes

Write a clear and concise description that helps reviewers understand the purpose and impact of your changes. Use the
following format:

Problem: Give a brief overview of the problem or feature being addressed.

Solution: Explain the approach you took to implement the solution, highlighting any significant design decisions or
considerations.

Testing: Describe any testing that you did.

Please focus on (optional): If you any specific areas where you would like reviewers to focus their attention or provide
specific feedback, add them here.

Closes #ISSUE

Checklist

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• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

Release notes

If this PR introduces a change that affects users and needs to be mentioned in the release notes,
please add a brief note that summarizes the change.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.76%. Comparing base (6022fce) to head (b47fe13).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3414      +/-   ##
==========================================
- Coverage   86.79%   86.76%   -0.04%     
==========================================
  Files         127      127              
  Lines       15020    15020              
  Branches       62       62              
==========================================
- Hits        13037    13032       -5     
- Misses       1833     1837       +4     
- Partials      150      151       +1     

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