getCoreProviders should return core providers only.

src/generators/crud/ProviderTrait.php

@@ -22,10 +22,11 @@ trait ProviderTrait
     public static function getCoreProviders()
     {
         $files = FileHelper::findFiles(
-            __DIR__.DIRECTORY_SEPARATOR.'providers', [
+            __DIR__.DIRECTORY_SEPARATOR.'providers/core',
+            [
                 'only' => ['*.php'],
-                'recursive' => true,
-                ]
+                'recursive' => false,
+            ]
         );
 
         foreach ($files as $file) {