ci/task-board: drop explicit container, inherit runner default

Runner is now re-registered with `:docker://node:20-bookworm-slim`
schema in its labels, so workflows targeting `pfi-fleet` get that
image automatically. Saves a few lines per workflow and gives us one
place (the runner config) to bump the default image when a new
node/debian release lands.

stacks/task-board/gitea-workflow-deploy.yaml.example

@@ -36,17 +36,12 @@ jobs:
   deploy:
     # `pfi-fleet` matches the central runner on ana-docker. Pin to
     # `ana-docker` instead if you want to refuse running on a future
-    # site-local runner.
+    # site-local runner. The runner's label embeds a default image
+    # (node:20-bookworm-slim) — has node + git out of the box, so
+    # actions/checkout@v4 (a JS action) works without a custom
+    # container. We just apt-install python3 + pyyaml for elway.
     runs-on: pfi-fleet
 
-    # Explicit container is required until the runner is re-registered
-    # with docker-schema labels (the initial `.runner` registration
-    # cached `:host` mode and that's sticky). node:20-bookworm-slim is
-    # ~150 MB, has node (so actions/checkout@v4 works) + apt
-    # (so we can install python3 + pyyaml for elway).
-    container:
-      image: node:20-bookworm-slim
-
     steps:
       - name: Install playbook prerequisites
         run: |