ci: bump ci to golang 1.20

[sozercan]

What this PR does / why we need it:
updates CI to Go 1.20

Which issue(s) this PR fixes (optional, using fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when the PR gets merged):
Fixes #2569

Special notes for your reviewer:

[sozercan]

The math/rand package now automatically seeds the global random number generator (used by top-level functions like Float64 and Int) with a random value, and the top-level Seed function has been deprecated.

https://tip.golang.org/doc/go1.20

[sozercan]

@maxsmythe @ritazh PTAL when you get a chance

[ritazh]

LGTM

[codecov-commenter]

Codecov Report

❌ Patch coverage is 46.34146% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 53.11%. Comparing base (df9a9d9) to head (34a4cf6).
⚠️ Report is 713 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/gator/verify/printer_go.go	0.00%	14 Missing ⚠️
pkg/gator/reader/read_constraints.go	0.00%	6 Missing ⚠️
pkg/gator/verify/runner.go	80.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2597      +/-   ##
==========================================
- Coverage   53.17%   53.11%   -0.06%     
==========================================
  Files         120      120              
  Lines       10569    10569              
==========================================
- Hits         5620     5614       -6     
- Misses       4513     4518       +5     
- Partials      436      437       +1     

Flag	Coverage Δ
unittests	53.11% <46.34%> (-0.06%)	⬇️

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