update codecov to v7

[clmould]

Description

See codecov/codecov-action#1956

Checklist

I confirm that I have completed the following checks:

• My changes follow the PROCESS style guide
• I have justified any large differences in the regression tests caused by this pull request in the comments.
• I have added new tests where appropriate for the changes I have made.
• If I have had to change any existing unit or integration tests, I have justified this change in the pull request comments.
• If I have made documentation changes, I have checked they render correctly.
• I have added documentation for my change, if appropriate.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 48.76%. Comparing base (d86c108) to head (3ed5b1d).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4302      +/-   ##
==========================================
+ Coverage   48.69%   48.76%   +0.06%     
==========================================
  Files         151      151              
  Lines       29290    29328      +38     
==========================================
+ Hits        14263    14301      +38     
  Misses      15027    15027              

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