lib/stm32wb/hci: app_conf.h: Re-apply patch Z-WB-3

When updating stm32wb hci lib from V1.12.0 to V1.13.0,
Zephyr specific patch Z-WB-3 (which configures BLE controller
firmware to work in mode LL only) was overwitten.
As a consequence, it was not possible to establish BLE connection
anymore.
Set it back.

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>