Updated migrations test to rollback to different versions

no issue

- in 4.0, we don't expect to rollback to 3.0 because there are
  irreversible migrations
- the existing test attempts to do this because it was written for v3
- this commit updates the test to apply to v4, although this will need
  to change soon when we switch branches

.github/workflows/test.yml

@@ -66,7 +66,13 @@ jobs:
       - run: |
           node index.js &
           sleep 20 && { kill $! && wait $!; } 2>/dev/null
+
+      - run: yarn knex-migrator rollback --v 4.0 --force
+        if: github.ref == 'refs/heads/4.0'
+
       - run: yarn knex-migrator rollback --v 3.0 --force
+        if: github.ref == 'refs/heads/master'
+
       - run: yarn knex-migrator migrate --force
 
   test: