chore(ci): bump go to 1.20

[pmalek]

What this PR does / why we need it:

Bump Go on CI to 1.20

[codecov]

Codecov Report

Base: 72.5% // Head: 72.5% // Increases project coverage by +0.0% 🎉

Coverage data is based on head (7906953) compared to base (66860b9).
Patch has no changes to coverable lines.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3540   +/-   ##
=====================================
  Coverage   72.5%   72.5%           
=====================================
  Files        123     122    -1     
  Lines      14384   14382    -2     
=====================================
- Hits       10429   10428    -1     
+ Misses      3291    3290    -1     
  Partials     664     664           

Impacted Files	Coverage Δ
...nternal/controllers/gateway/udproute_controller.go	71.6% <0.0%> (-2.2%)	⬇️
...ternal/controllers/gateway/httproute_controller.go	69.7% <0.0%> (-1.9%)	⬇️
internal/dataplane/kongstate/service.go	66.0% <0.0%> (-1.3%)	⬇️
internal/cmd/main.go
internal/store/store.go	66.2% <0.0%> (+0.4%)	⬆️
...nternal/controllers/gateway/tlsroute_controller.go	73.4% <0.0%> (+2.0%)	⬆️
internal/dataplane/parser/translate_tlsroute.go	64.0% <0.0%> (+6.7%)	⬆️

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