Remove readme project_view option

Fixes issue introduced by https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11191.

Not caught earlier because the 'Readme' project view can no longer be selected in Profile Settings > Preferences, but there may still be User records with this value for project_view.

app/assets/javascripts/dispatcher.js

@@ -261,6 +261,8 @@ const ShortcutsBlob = require('./shortcuts_blob');
           new NotificationsForm();
           if ($('#tree-slider').length) {
             new TreeView();
+          }
+          if ($('.blob-viewer').length) {
             new BlobViewer();
           }
           break;