Don't show deploy instructions for forked builds

Author: aequitas

.github/workflows/docker.yml

@@ -227,6 +227,10 @@ jobs:
           retention-days: 1
 
   docs:
+    # if this build is for a forked PR or dependabot the images are not pushed to the
+    # registry and the deploy instructions won't work.
+    if: ${{ env.use_registry == 'false' }}
+
     runs-on: ubuntu-22.04
     needs: [build-docker]
     steps: