Removed 'Hide already enrolled' checkbox.

The 'Hide already enrolled' has been removed from the enrollment
dialog because it is checked by default and entries that are already
enrolled cannot be enrolled again.

Ticket #1638

ipalib/plugins/internal.py

@@ -355,7 +355,6 @@ class i18n_messages(Command):
             "confirmation":_("Confirmation"),
             "dirty_message":_("This page has unsaved changes. Please save or revert."),
             "dirty_title":_("Dirty"),
-            "hide_already_enrolled":_("Hide already enrolled."),
             "hide_details":_("Hide details"),\
             "redirection":_("Redirection"),
             "remove_empty":_("Select entries to be removed."),