ci release: remove garbage

Author: kou

.github/workflows/release.yml

@@ -35,7 +35,7 @@ jobs:
           mv dist ${GRAFANA_PLUGIN_ID}
           zip -r ${GRAFANA_PLUGIN_ARTIFACT} ${GRAFANA_PLUGIN_ID}
           md5sum ${GRAFANA_PLUGIN_ARTIFACT} > ${GRAFANA_PLUGIN_ARTIFACT_CHECKSUM}
-          echo "GRAFANA_PLUGIN_CHECKSUM=$(cat ${GRAFANA_PLUGIN_ARTIFACT_CHECKSUM})" >> ${GITHUB_ENV}
+          echo "GRAFANA_PLUGIN_CHECKSUM=$(cut -d' ' -f1 ${GRAFANA_PLUGIN_ARTIFACT_CHECKSUM})" >> ${GITHUB_ENV}
       - name: Create release
         id: create-release
         uses: actions/create-release@v1