chore(deps): update golang docker tag to v1.21

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
golang	final	minor	1.20 -> 1.21

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[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (20a0700) 73.50% compared to head (391eaf8) 73.50%.

❗ Current head 391eaf8 differs from pull request most recent head 13b9c53. Consider uploading reports for the commit 13b9c53 to get more accurate results

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Additional details and impacted files

@@           Coverage Diff           @@
##           master     #265   +/-   ##
=======================================
  Coverage   73.50%   73.50%           
=======================================
  Files          43       43           
  Lines        2291     2291           
=======================================
  Hits         1684     1684           
  Misses        377      377           
  Partials      230      230           

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