Drop explicit docker.sock mount — runner auto-injects it

ba-runner already binds /var/run/docker.sock into every job container,
so declaring it in the workflow caused a Duplicate mount point error.
Keep the docker:27-cli image; let the runner provide the socket.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitea/workflows/flow.yml

@@ -32,8 +32,6 @@ jobs:
     runs-on: ubuntu-latest
     container:
       image: docker:27-cli
-      volumes:
-        - /var/run/docker.sock:/var/run/docker.sock
     outputs:
       image_tag: ${{ steps.meta.outputs.tag }}
     steps: