fix pulling secrets in cloudbuild release for latest builds

[IsaacPD]

Related: #5314

Description
Applies the changes of cloudbuild-release.yaml in #5314 to cloudbuild.yaml to fix the "Skaffold latest build" trigger. This trigger keeps failing with

Starting Step #0
Step #0: Already have image (with digest): gcr.io/cloud-builders/gsutil
Step #0: CommandException: Destination URL must name a directory, bucket, or bucket
Step #0: subdirectory for the multiple source form of the cp command.
Finished Step #0
ERROR
ERROR: build step 0 "gcr.io/cloud-builders/gsutil" failed: step exited with non-zero status: 1

since it was not modified to properly pull the keys from the gcs bucket. Uses deploy/setup-secret.sh instead to pull the secret.

[codecov]

Codecov Report

Merging #5328 (68a2526) into master (7a326e6) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #5328   +/-   ##
=======================================
  Coverage   71.79%   71.79%           
=======================================
  Files         390      390           
  Lines       14215    14215           
=======================================
  Hits        10206    10206           
  Misses       3257     3257           
  Partials      752      752           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7a326e6...68a2526. Read the comment docs.