ci: do explicit fetch

Author: id

.github/workflows/sync-en-doc.yaml

@@ -51,6 +51,7 @@ jobs:
           git config --global user.email "${GITHUB_ACTOR}@users.noreply.github.com"
           BASE_BRANCH="$(echo v$(echo $EMQX_VERSION | awk -F. '{print $1$2}'))"
           NEW_BRANCH="sync-${EMQX_VERSION}"
+          git fetch origin
           git checkout -b ${NEW_BRANCH} --track origin/${BASE_BRANCH}
           cp _build/docgen/emqx-enterprise/desc.en.hocon ./
           git add desc.en.hocon