DevKit updates (#4170)

.styleci.yml

@@ -7,6 +7,7 @@
 preset: symfony
 
 enabled:
+  - class_keyword_remove
   - combine_consecutive_unsets
   - long_array_syntax
   - newline_after_open_tag

CONTRIBUTING.md

@@ -181,9 +181,9 @@ namespace Foo;
 
 interface BarInterface
 {
-
-  // NEXT_MAJOR: Uncomment this method
   /**
+   * NEXT_MAJOR: Uncomment this method
+   *
    * This method does useful stuff.
    */
   // public function usefulMethod();