Drop explicit docker.sock mount — act_runner auto-mounts it (was duplicate)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.forgejo/workflows/docker-build.yml

@@ -13,13 +13,11 @@ jobs:
     # Runner offers ubuntu-latest; the label only selects the runner. The job
     # overrides the image below with docker:cli and mounts the host socket.
     runs-on: ubuntu-latest
-    # Run the job in a Docker-CLI container and mount the host's Docker socket
-    # (OrbStack) so `docker build` talks to the host daemon. Requires the runner
-    # config to allow this volume — see valid_volumes note.
+    # Run the job in a Docker-CLI container. act_runner already auto-mounts the
+    # host Docker socket (OrbStack), so `docker` reaches the host daemon — don't
+    # mount it again here or Docker errors with "Duplicate mount point".
     container:
       image: docker:cli
-      volumes:
-        - /var/run/docker.sock:/var/run/docker.sock
     steps:
       - name: Install git
         run: apk add --no-cache git