ci: update docker image version for docs

.gitlab-ci.yml

@@ -58,7 +58,7 @@ variables:
   CI_AUTO_TEST_SCRIPT_REPO_BRANCH: "ci/v3.1"
 
   # Versioned esp-idf-doc env image to use for all document building jobs
-  ESP_IDF_DOC_ENV_IMAGE: "$CI_DOCKER_REGISTRY/esp-idf-doc-env:v9-4a53df18"
+  ESP_IDF_DOC_ENV_IMAGE: "$CI_DOCKER_REGISTRY/esp-idf-doc-env:v9"
 
 .setup_tools_unless_target_test: &setup_tools_unless_target_test |
   if [[ -n "$IDF_DONT_USE_MIRRORS" ]]; then