Use existing functions from xdg-go/scram pkg

[yurishkuro]

Clean-up for #2046

[codecov]

Codecov Report

Merging #3481 (4785764) into main (179073f) will increase coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #3481      +/-   ##
==========================================
+ Coverage   96.44%   96.49%   +0.05%     
==========================================
  Files         262      262              
  Lines       15311    15311              
==========================================
+ Hits        14766    14774       +8     
+ Misses        460      454       -6     
+ Partials       85       83       -2     

Impacted Files	Coverage Δ
cmd/query/app/server.go	95.58% <0.00%> (+1.47%)	⬆️
cmd/query/app/static_handler.go	95.80% <0.00%> (+1.79%)	⬆️
pkg/config/tlscfg/cert_watcher.go	94.73% <0.00%> (+2.10%)	⬆️

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