fix: print warnings to stderr (#8342)

cli/cli-utils/src/getConfig.ts

@@ -28,9 +28,8 @@ export async function getConfig (
     delete config.reporter // This is a silly workaround because @pnpm/core expects a function as opts.reporter
   }
 
-  // The warning should not be printed when --json is specified
-  if (warnings.length > 0 && !cliOptions.json) {
-    console.log(warnings.map((warning) => formatWarn(warning)).join('\n'))
+  if (warnings.length > 0) {
+    console.warn(warnings.map((warning) => formatWarn(warning)).join('\n'))
   }
 
   return config