update builder to use go1.21

[cpanato]

Summary

• update builder to use go1.21

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (ddeeb3f) 66.39% compared to head (e7f4754) 47.60%.
Report is 3 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1956       +/-   ##
===========================================
- Coverage   66.39%   47.60%   -18.79%     
===========================================
  Files          92       92               
  Lines        9197     9197               
===========================================
- Hits         6106     4378     -1728     
- Misses       2347     3943     +1596     
- Partials      744      876      +132     

Flag	Coverage Δ
e2etests	47.60% <ø> (ø)
unittests	?

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.