test: collect garbage

Author: samrose

.github/workflows/test.yml

@@ -81,6 +81,7 @@ jobs:
           echo "EOF" >> $GITHUB_OUTPUT
       - name: verify schema.sql is committed
         run: |
+          nix-collect-garbage -d
           nix run github:supabase/postgres/${{ github.sha }}#dbmate-tool -- --version ${{ env.PGMAJOR }} --flake-url github:supabase/postgres/${{ github.sha }}
           if ! git diff --exit-code --quiet migrations/schema-${{ env.PGMAJOR }}.sql; then
             echo "Detected changes in schema.sql:"