chore: try with flake url to target current changes

Author: samrose

.github/workflows/test.yml

@@ -76,7 +76,7 @@ jobs:
           echo "EOF" >> $GITHUB_OUTPUT
       - name: verify schema.sql is committed
         run: |
-          nix run github:supabase/postgres/${{ github.sha }}#dbmate-tool -- --version ${{ env.PGMAJOR }}
+          nix run github:supabase/postgres/${{ github.sha }}#dbmate-tool -- --version ${{ env.PGMAJOR }} --flake-url github:supabase/postgres/${{ github.sha }}
           if ! git diff --exit-code --quiet migrations/schema-${{ env.PGMAJOR }}.sql; then
             echo "Detected changes in schema.sql:"
             git diff migrations/schema-${{ env.PGMAJOR }}.sql