ci: Create test-docs job in mesa/mesa pipelines for MRs

Since the last GitLab update, pre-merge pipelines for MRs run in the
mesa/mesa namespace, so this job didn't get created anymore, causing
trouble.

Reviewed-by: Daniel Stone <daniels@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6522>
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 07fdd5e..13a9cae 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -70,11 +70,12 @@
   stage: container+docs
   rules:
     - *ignore_scheduled_pipelines
-    - if: '$CI_PROJECT_NAMESPACE == "mesa"'
-      when: never
     - if: '$GITLAB_USER_LOGIN == "marge-bot" && $CI_MERGE_REQUEST_SOURCE_BRANCH_NAME == $CI_COMMIT_REF_NAME'
       changes: *docs-or-ci
       when: on_success
+    - if: '$GITLAB_USER_LOGIN != "marge-bot" && $CI_MERGE_REQUEST_SOURCE_BRANCH_NAME != $CI_COMMIT_REF_NAME && $CI_PROJECT_PATH == "mesa/mesa"'
+      changes: *docs-or-ci
+      when: on_success
     - changes: *docs-or-ci
       when: manual
     # Other cases default to never