Remove unused/broken require in site.js

I broke this in f7b519d, it seems.

h/static/scripts/site.js

@@ -9,7 +9,6 @@ var page = require('page');
 var CreateGroupFormController = require('./create-group-form');
 var DropdownMenuController = require('./dropdown-menu');
 var InstallerController = require('./installer-controller');
-var ShareGroupFormController = require('./share-group-form');
 
 // setup components
 new DropdownMenuController(document);