dprint-plugins: disable automatic config discovery

The opt‑out switch was added in dprint 0.50.0.

pkgs/by-name/dp/dprint/plugins/default.nix

···
         runHook preInstallCheck
 
         mkdir empty && cd empty
-        dprint check --allow-no-files --plugins "$out/plugin.wasm"
+        dprint check --allow-no-files --config-discovery=false --plugins "$out/plugin.wasm"
 
         runHook postInstallCheck
       '';