fix: disable push of pull requests to ghcr.io

.gitlab-ci.yml

@@ -114,6 +114,7 @@ version:
         NIGHTLY_TAG="${VERSION}-nightly"
         EXPORT_TAG="${VERSION}"
         DH_PUSH=""
+        GH_PUSH=""
       elif [ "x${CI_PIPELINE_SOURCE}" = "xtrigger" ]; then
         VERSION="${CI_COMMIT_BRANCH}"
         DH_PUSH=""