fix(docs-bootstrap): Removed injector from bootstrapped docs samples

This is necessary to make e2e tests pass for implementing #3411. At present, the docs are violating the rule being enforced by double-bootstrap prevention.

docs/components/angular-bootstrap/bootstrap-prettify.js

@@ -241,6 +241,7 @@ directive.ngEmbedApp = ['$templateCache', '$browser', '$rootScope', '$location',
         embedRootScope.$destroy();
       });
 
+      element.data('$injector', null);
       angular.bootstrap(element, modules);
     }
   };