fix(mod/dashboard): use deleteKey() not delete_key()

small bug I overlooked while refactoring all of the dashboard function
names to be more "javascripty"

mod/dashboard/app/scripts/controllers/browser.js

@@ -113,7 +113,7 @@ angular.module('etcdBrowser', ['ngRoute', 'etcd', 'timeRelative'])
     }).error(function (data, status, headers, config) {
       //TODO: remove loader
       //show errors
-      $scope.showBrowseError('Error: Could not delete the key');
+      $scope.showBrowseError('Could not delete the key');
     });
   };