samples: wifi: ble_coex: Fix for Wi-Fi connection issue

pbkdf2_sha1 returned error due to malloc failures while configuring
PSK. Increase MBEDTLS_HEAP_SIZE to fix this.

Signed-off-by: Murali Thokala <[email protected]>

Author: muraliThokala

samples/wifi/ble_coex/prj.conf

@@ -116,3 +116,4 @@ CONFIG_NRF70_QSPI_LOW_POWER=n
 #Added to fix BLE crash in coex enable cases.
 CONFIG_NRF_RPC=n
 CONFIG_NRF_RPC_CBOR=n
+CONFIG_MBEDTLS_HEAP_SIZE=1024