Revert "samples: bt: reduce system heap memory for the hci_ipc sample"

This reverts commit 184c0f9.

Reducing system heap memory to 1024 caused runtime failures on some
platforms. This commit revert that change and return to the previous
size.

Signed-off-by: Valerio Setti <[email protected]>

Author: valeriosetti

samples/bluetooth/hci_ipc/nrf5340_cpunet_iso-bt_ll_sw_split.conf

@@ -5,7 +5,7 @@ CONFIG_ISR_STACK_SIZE=1024
 CONFIG_IDLE_STACK_SIZE=256
 CONFIG_MAIN_STACK_SIZE=512
 CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=512
-CONFIG_HEAP_MEM_POOL_SIZE=1024
+CONFIG_HEAP_MEM_POOL_SIZE=4096
 CONFIG_CBPRINTF_REDUCED_INTEGRAL=y
 
 CONFIG_ISR_TABLES_LOCAL_DECLARATION=y