docs($interpolateProvider): remove superfluous ng-app attribute

The example processor is adding the module attr in the example tag as
the ng-app attr on the body.

Closes #13608

Author: Narretz

src/ng/interpolate.js

@@ -21,7 +21,7 @@ $interpolateMinErr.interr = function(text, err) {
  * Used for configuring the interpolation markup. Defaults to `{{` and `}}`.
  *
  * @example
-<example module="customInterpolationApp">
+<example name="custom-interpolation-markup" module="customInterpolationApp">
 <file name="index.html">
 <script>
   var customInterpolationApp = angular.module('customInterpolationApp', []);
@@ -36,7 +36,7 @@ $interpolateMinErr.interr = function(text, err) {
       this.label = "This binding is brought you by // interpolation symbols.";
   });
 </script>
-<div ng-app="App" ng-controller="DemoController as demo">
+<div ng-controller="DemoController as demo">
     //demo.label//
 </div>
 </file>