Update sonarcloud.yml with the condition for this repo instance

[stan-dot]

The sonarcloud workflow requires an auth key, so will not work with PRs from forks, which we want to support. We will therefore skip that job when the PR is from a fork.

thanks @callumforrester

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.62%. Comparing base (627ffc3) to head (d0bbe44).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #664   +/-   ##
=======================================
  Coverage   92.62%   92.62%           
=======================================
  Files          35       35           
  Lines        1654     1654           
=======================================
  Hits         1532     1532           
  Misses        122      122           

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[callumforrester]

Just to quickly document the reasons: The sonarcloud workflow requires an auth key, so will not work with PRs from forks, which we want to support. We will therefore skip that job when the PR is from a fork.