samples: nrfcloud_multi_service: Increase heap t91x

Provisioning not working, calloc failure on jwt generation. Increase
heap to fix.

Signed-off-by: Jorgen Kvalvaag <jorgen.kvalvaag@nordicsemi.no>

samples/cellular/nrf_cloud_multi_service/boards/thingy91x_nrf9151_ns.conf

@@ -64,7 +64,7 @@ CONFIG_NET_RX_STACK_SIZE=512
 CONFIG_NET_TC_TX_COUNT=1
 CONFIG_NET_MAX_CONTEXTS=5
 
-CONFIG_HEAP_MEM_POOL_SIZE=20000
+CONFIG_HEAP_MEM_POOL_SIZE=22000
 CONFIG_HEAP_MEM_POOL_IGNORE_MIN=y
 CONFIG_MAIN_STACK_SIZE=2048
 CONFIG_NET_MGMT_EVENT_STACK_SIZE=1024