docs(ngInclude): replace <tt> with <code>

Using obsolete <tt> HTML tag may not be good for Angular examples

Closes #10594

src/ng/directive/ngInclude.js

@@ -49,7 +49,7 @@
        <select ng-model="template" ng-options="t.name for t in templates">
         <option value="">(blank)</option>
        </select>
-       url of the template: <tt>{{template.url}}</tt>
+       url of the template: <code>{{template.url}}</code>
        <hr/>
        <div class="slide-animate-container">
          <div class="slide-animate" ng-include="template.url"></div>