ci: use our cached oci images

.forgejo/workflows/cascade-setup-forgejo.yml

@@ -8,6 +8,8 @@ on:
 jobs:
   cascade:
     runs-on: docker
+    container:
+      image: 'code.forgejo.org/oci/node:20-bookworm'
     if: vars.CASCADE != 'no'
     steps:
       - uses: actions/cascading-pr@v1

.forgejo/workflows/test.yml

@@ -19,6 +19,8 @@ jobs:
     name: build and test
     if: github.repository_owner != 'forgejo-integration' && github.repository_owner != 'forgejo-experimental' && github.repository_owner != 'forgejo-release'
     runs-on: docker
+    container:
+      image: 'code.forgejo.org/oci/node:20-bookworm'
 
     services:
       forgejo: