chore(deps): update alpine docker tag to v3.21.0

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
alpine	final	minor	3.18.4 -> 3.21.0

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.98%. Comparing base (0847956) to head (e664954).
Report is 1 commits behind head on main.

❗ Current head e664954 differs from pull request most recent head 21b06ec

Please upload reports for the commit 21b06ec to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #140      +/-   ##
==========================================
- Coverage   80.14%   79.98%   -0.16%     
==========================================
  Files          27       27              
  Lines        1919     1919              
==========================================
- Hits         1538     1535       -3     
- Misses        312      314       +2     
- Partials       69       70       +1     

Flag	Coverage Δ
unittests	79.98% <ø> (-0.16%)	⬇️

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