chore(deps): update docker.io/library/golang docker tag to v1.21.4

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
docker.io/library/golang	stage	patch	1.21.3 -> 1.21.4

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[codecov]

Codecov Report

Merging #59 (1301abc) into main (247eb0d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #59   +/-   ##
=======================================
  Coverage   50.47%   50.47%           
=======================================
  Files           5        5           
  Lines         424      424           
=======================================
  Hits          214      214           
  Misses        185      185           
  Partials       25       25