Add NEWS entry for GH-21362 Reflection Closure identity fix

Author: iliaal

NEWS

@@ -90,6 +90,8 @@ PHP                                                                        NEWS
   . Added ReflectionConstant::inNamespace(). (Khaled Alam)
   . Added ReflectionProperty::isReadable() and ReflectionProperty::isWritable().
     (ilutov)
+  . Fixed bug GH-21362 (ReflectionMethod::invoke/invokeArgs() did not verify
+    Closure instance identity for Closure::__invoke()). (Ilia Alshanetsky)
 
 - Session:
   . Fixed bug 71162 (updateTimestamp never called when session data is empty).