ci: fix image verification

Author: janfuhrer

.github/workflows/release.yml

@@ -142,7 +142,6 @@ jobs:
           cosign verify \
             --certificate-oidc-issuer https://token.actions.githubusercontent.com \
             --certificate-identity-regexp '^https://github.com/natrontech/gcp-mysql-backup/.github/workflows/release.yml@refs/.*$' \
-            --certificate-identity-regexp '^https://github.com/natrontech/gcp-mysql-backup/.github/workflows/release.yml@refs/heads/main$' \
             $IMAGE@$DIGEST
 
       - name: Verify sbom of image