refactor(ngMessage): remove unused argument

Closes angular#13087
Closes angular#12508

Author: gkalpak

src/ngMessages/messages.js

@@ -565,7 +565,7 @@ angular.module('ngMessages', [])
     *
     * @param {expression} ngMessage|when a string value corresponding to the message key.
     */
-  .directive('ngMessage', ngMessageDirectiveFactory('AE'))
+  .directive('ngMessage', ngMessageDirectiveFactory())
 
 
    /**
@@ -597,9 +597,9 @@ angular.module('ngMessages', [])
     *
     * @param {expression} ngMessageExp|whenExp an expression value corresponding to the message key.
     */
-  .directive('ngMessageExp', ngMessageDirectiveFactory('A'));
+  .directive('ngMessageExp', ngMessageDirectiveFactory());
 
-function ngMessageDirectiveFactory(restrict) {
+function ngMessageDirectiveFactory() {
   return ['$animate', function($animate) {
     return {
       restrict: 'AE',