Revert "Switched to Node.js container in Action"

- this reverts commit 3e3a2af71a.
- the tests require more components than Node, which the container
  doesn't have

ghost/admin/.github/workflows/test.yml

@@ -8,7 +8,6 @@ on:
 jobs:
   test:
     runs-on: ubuntu-latest
-    container: node:10
     if: github.event_name == 'push' || (github.event_name == 'pull_request' && !startsWith(github.head_ref, 'renovate/'))
     strategy:
       matrix:
@@ -20,6 +19,9 @@ jobs:
       CI: true
     steps:
       - uses: actions/checkout@v2
+      - uses: actions/setup-node@v1
+        with:
+          node-version: 10
       - run: yarn
       - run: yarn lint:js
       - run: yarn test