vt: Delete comment referencing non-existent unbind_con_driver()

Commit c1f5e38a ("vt: delete unneeded function unbind_con_driver")
removed unbind_con_driver() but retained a comment referencing the
function.  Delete it.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Wang YanQing <udknight@gmail.com>
Link: https://lore.kernel.org/r/4d77a67d77a1c699e9a6cc3e73044c31c02d60b5.1578574427.git.lukas@wunner.de


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>