ci: tweak translation task's PR title

Author: seratch

.github/workflows/update-docs.yml

@@ -78,7 +78,7 @@ jobs:
         uses: peter-evans/create-pull-request@v8
         with:
           commit-message: "Update translated document pages"
-          title: "Update translated document pages"
+          title: "docs: update translated document pages"
           body: |
             Automated update of translated documentation.