xProfile: remove unused param from wp-admin JS `enableSortableFieldOptions()` function.

Recent changes in r8642 made this variable unused, and it's causing jshint errors.

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8648 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Merge branch 'master' into mentions-js