[make:user] add the void return type to eraseCredentials()

Author: jrushlow

src/Security/UserClassBuilder.php

@@ -304,7 +304,7 @@ private function addEraseCredentials(ClassSourceManipulator $manipulator): void
         // add eraseCredentials: always empty
         $builder = $manipulator->createMethodBuilder(
             'eraseCredentials',
-            null,
+            'void',
             false,
             ['@see UserInterface']
         );