Bluetooth: samples: Remove workqueue stack configuration

Fixed value used is too low causing overflow in nrf53.  Use default
value instead.

Signed-off-by: Azizah Ibrahim <[email protected]>

Author: ibaz-nordic

samples/bluetooth/hci_pwr_ctrl/prj.conf

@@ -1,7 +1,6 @@
 CONFIG_BT=y
 CONFIG_BT_DEBUG_LOG=y
 CONFIG_BT_PERIPHERAL=y
-CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=768
 CONFIG_BT_HRS=y
 CONFIG_BT_DEVICE_APPEARANCE=833
 CONFIG_BT_DEVICE_NAME="Dynamic test beacon"