replace NewClient with NewRegistryClient

[theganyo]

Fixes #660

[codecov]

Codecov Report

Merging #665 (9e92bcb) into main (62bdd9f) will not change coverage.
The diff coverage is 40.00%.

❗ Current head 9e92bcb differs from pull request most recent head 43891ea. Consider uploading reports for the commit 43891ea to get more accurate results

@@           Coverage Diff           @@
##             main     #665   +/-   ##
=======================================
  Coverage   53.91%   53.91%           
=======================================
  Files          77       77           
  Lines        7222     7222           
=======================================
  Hits         3894     3894           
  Misses       2914     2914           
  Partials      414      414           

Impacted Files	Coverage Δ
cmd/registry/cmd/compute/complexity.go	0.00% <0.00%> (ø)
cmd/registry/cmd/compute/lint.go	0.00% <0.00%> (ø)
cmd/registry/cmd/compute/lintstats.go	0.00% <0.00%> (ø)
cmd/registry/cmd/compute/references.go	0.00% <0.00%> (ø)
cmd/registry/cmd/compute/score.go	0.00% <0.00%> (ø)
cmd/registry/cmd/compute/scorecard.go	0.00% <0.00%> (ø)
cmd/registry/cmd/compute/vocabulary.go	0.00% <0.00%> (ø)
cmd/registry/cmd/export/sheet.go	7.92% <0.00%> (ø)
cmd/registry/cmd/export/yaml.go	15.68% <0.00%> (ø)
cmd/registry/cmd/upload/spec.go	13.39% <0.00%> (ø)
... and 13 more

[timburks]

I filed this issue about the doc.go problem.