ci: don't run tests twice in coverage

[DaniPopes]

Motivation

Build only step is unnecessary because we already have it in the tests CI, and also it runs the tests without a convenient way (that I know of) to only build them, so remove it.
Also it runs

Solution

PR Checklist

• Added Tests
• Added Documentation
• Updated the changelog

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.02% ⚠️

Comparison is base (e34200e) 82.74% compared to head (623c297) 82.73%.
Report is 2 commits behind head on main.

❗ Current head 623c297 differs from pull request most recent head ef9ef16. Consider uploading reports for the commit ef9ef16 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #278      +/-   ##
==========================================
- Coverage   82.74%   82.73%   -0.02%     
==========================================
  Files          52       52              
  Lines        5588     5588              
==========================================
- Hits         4624     4623       -1     
- Misses        964      965       +1     

see 1 file with indirect coverage changes

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