Fix parameter name in exception for case when Kernel has custom namespace (#199)

Author: prophetz

src/Codeception/Module/Symfony.php

@@ -321,7 +321,7 @@ protected function getKernelClass(): string
         throw new ModuleRequireException(
             self::class,
             "Kernel class was not found.\n"
-            . 'Specify directory where file with Kernel class for your application is located with `app_path` parameter.'
+            . 'Specify directory where file with Kernel class for your application is located with `kernel_class` parameter.'
         );
     }