Bluetooth: Remove redundant (and possibly wrong) flag clearing

There's no need to clear the HCI_CONN_ENCRYPT_PEND flag in
smp_failure. In fact, this may cause the encryption tracking to get
out of sync as this has nothing to do with HCI activity.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>