chore(ngModelOptions): remove reference to angular.copy

Replaced a reference to `angular.copy` with just `copy`

Author: lgalfaso

src/ng/directive/ngModel.js

@@ -1215,7 +1215,7 @@ var ngModelOptionsDirective = function() {
     restrict: 'A',
     controller: ['$scope', '$attrs', function($scope, $attrs) {
       var that = this;
-      this.$options = angular.copy($scope.$eval($attrs.ngModelOptions));
+      this.$options = copy($scope.$eval($attrs.ngModelOptions));
       // Allow adding/overriding bound events
       if (this.$options.updateOn !== undefined) {
         this.$options.updateOnDefault = false;