remove cosign gh checks due to job removal

[cpanato]

Summary

• remove cosign gh checks due to job removal

need this to be able to merge: sigstore/cosign#3629

[github-actions]

🍹 preview on sigstore-github-sync/sigstore/github-prod

Pulumi report

Previewing update (sigstore/github-prod)

View Live: https://app.pulumi.com/sigstore/sigstore-github-sync/github-prod/previews/ab3225a6-d3d8-4dab-a726-eeddc4f19c06

@ Previewing update.....
pulumi:pulumi:Stack: (same)
[urn=urn:pulumi:github-prod::sigstore-github-sync::pulumi:pulumi:Stack::sigstore-github-sync-github-prod]
~ github:index/branchProtection:BranchProtection: (update)
    [id=BPR_kwDOFAY6Ic4B9d__]
    [urn=urn:pulumi:github-prod::sigstore-github-sync::github:index/branchProtection:BranchProtection::cosign-main]
  ~ requiredStatusChecks: [
      ~ [0]: {
              ~ contexts: [
                  - [0]: "build (ubuntu-latest)"
                  - [9]: "build (macos-latest)"
                  - [14]: "build (windows-latest)"
                ]
            }
    ]
Resources:
~ 1 to update
584 unchanged