Use forgejo mirror images

.forgejo/testdata/ipv6.yml

@@ -4,7 +4,7 @@ jobs:
   ipv6:
     runs-on: docker
     container:
-      image: debian:bookworm
+      image: code.forgejo.org/oci/debian:bookworm
     steps:
       - run: |
           apt update -qq ; apt --quiet install -qq --yes iputils-ping

.forgejo/workflows/example-docker-compose.yml

@@ -61,7 +61,7 @@ jobs:
           done
           grep --quiet "$success" /tmp/out
           $cli logs runner-daemon > /tmp/runner.log
-          grep --quiet 'Start image=node:20-bookworm' /tmp/runner.log
+          grep --quiet 'Start image=code.forgejo.org/oci/node:20-bookworm' /tmp/runner.log
 
       - name: full docker compose logs
         if: always()