Use stripslashes_deep() rather than wp_unslash() in bp-members-admin.php

The functions do the same thing, but wp_unslash() was not available prior to
WP 3.6.

See #5197

Props lenasterg

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7990 cdf35c40-ae34-48e0-9cc9-0c9da1808c22