chore: Upgrade to Golang 1.18

[terrytangyuan]

Signed-off-by: Yuan Tang terrytangyuan@gmail.com

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[codecov]

Codecov Report

Merging #9066 (9aef1c2) into master (edcd57a) will decrease coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #9066      +/-   ##
==========================================
- Coverage   45.48%   45.44%   -0.05%     
==========================================
  Files         217      217              
  Lines       25655    25655              
==========================================
- Hits        11669    11658      -11     
- Misses      12357    12371      +14     
+ Partials     1629     1626       -3     

Impacted Files	Coverage Δ
applicationset/services/scm_provider/github.go	63.52% <0.00%> (-17.65%)	⬇️
util/settings/settings.go	48.10% <0.00%> (ø)
applicationset/services/scm_provider/utils.go	88.50% <0.00%> (+4.59%)	⬆️

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[leoluz]

LGTM

[crenshaw-dev]

lgtm!