docs(guide/understanding-controllers): fix typo in example

Broken - $scope.spicy = 'very';
Works - $scope.spice = 'very';

Closes angular#4752

Author: joshbowdoin

docs/content/guide/dev_guide.mvc.understanding_controller.ngdoc

@@ -145,7 +145,7 @@ string "very". Depending on which button is clicked, the `spice` model is set to
       var myApp = angular.module('spicyApp1', []);
 
       myApp.controller('SpicyCtrl', ['$scope', function($scope){
-          $scope.spicy = 'very';
+          $scope.spice = 'very';
 
           $scope.chiliSpicy = function() {
               $scope.spice = 'chili';