CI: Add tolerance to reduce spurious codecov failures

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 90.52%. Comparing base (5cfeff2) to head (a32bb3a). Report is 2 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #122 +/- ## ======================================= Coverage 90.52% 90.52% ======================================= Files 85 85 Lines 6082 6082 Branches 611 611 ======================================= Hits 5506 5506 Misses 544 544 Partials 32 32 ```

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