bump ggcr dep to @main

[imjasonh]

go get -u github.com/google/go-containerregistry@main
go mod tidy
go mod vendor

[codecov-commenter]

Codecov Report

Merging #976 (fe22b3d) into main (8e075ae) will not change coverage.
The diff coverage is n/a.

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@@           Coverage Diff           @@
##             main     #976   +/-   ##
=======================================
  Coverage   52.50%   52.50%           
=======================================
  Files          43       43           
  Lines        3331     3331           
=======================================
  Hits         1749     1749           
  Misses       1353     1353           
  Partials      229      229           

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