remove unneeded calls to goimports when generating mocks

[marten-seemann]

gomock now correctly sorts imports, see golang/mock#458.

[codecov]

Codecov Report

Merging #3313 (7d5a7b4) into master (63b7354) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3313      +/-   ##
==========================================
+ Coverage   85.65%   85.66%   +0.01%     
==========================================
  Files         133      133              
  Lines        9786     9786              
==========================================
+ Hits         8382     8383       +1     
+ Misses       1029     1028       -1     
  Partials      375      375              

Impacted Files	Coverage Δ
internal/utils/rand.go	75.00% <0.00%> (+12.50%)	⬆️

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