Update tests.yml

[cescalara]

Update codecov version to avoid error: codecov/codecov-action#598

[codecov]

Codecov Report

Attention: Patch coverage is 84.84848% with 5 lines in your changes missing coverage. Please review.

Project coverage is 54.35%. Comparing base (d8f8bc2) to head (b4c5dc3).
Report is 9 commits behind head on master.

Files with missing lines	Patch %	Lines
icecube_tools/utils/data.py	84.84%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #58      +/-   ##
==========================================
- Coverage   55.52%   54.35%   -1.17%     
==========================================
  Files          24       24              
  Lines        4454     4465      +11     
==========================================
- Hits         2473     2427      -46     
- Misses       1981     2038      +57     

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