build: upgrade to go1.20.6

[algorandskiy]

Summary

1. use go1.20.6
2. revert go-expermiments disabling

Test Plan

Local runs showed no perf difference.

[codecov]

Codecov Report

Merging #5577 (1e531eb) into master (d316914) will decrease coverage by 0.03%.
Report is 34 commits behind head on master.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #5577      +/-   ##
==========================================
- Coverage   55.79%   55.76%   -0.03%     
==========================================
  Files         446      446              
  Lines       63418    63418              
==========================================
- Hits        35381    35365      -16     
- Misses      25668    25681      +13     
- Partials     2369     2372       +3     

see 18 files with indirect coverage changes

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[cce]

You also have to upgrade the versions in .github/workflows

[algobarb]

Maybe it needs to be run once with line 62 set to if: steps.cache-golangci-lint.outputs.cache-hit == 'true' in .github/workflows/reviewdog.yml. Then it will update the cache and afterwards, you can revert the change. (EDIT: or maybe the versions in .github/workflows/reviewdog.yml just need to be updated)

[algobarb]

LGTM