tests: bsim: bluetooth: mesh: Fix pb_cancel test

Enable retransmissions of Generic Provisioning PDUs. This should fix
pb_cancel test where provisionee fails to receive Link Open PDU due to
parallel PB-GATT advertisement, but since Link Open PDU is not
retransmitted, test fails.

Signed-off-by: Pavel Vasilyev <pavel.vasilyev@nordicsemi.no>

Author: PavelVPV

tests/bsim/bluetooth/mesh/overlay_gatt.conf

@@ -8,3 +8,8 @@ CONFIG_BT_MESH_PROXY_CLIENT=y
 CONFIG_BT_MESH_PROXY_SOLICITATION=y
 
 CONFIG_BT_BUF_CMD_TX_COUNT=3
+
+# Increase number of retransmissions for PB-ADV when running tests with PB-GATT. This is to avoid
+# test failures due to pb-adv packets loss by provisionee which runs PB-GATT in parallel with
+# PB-ADV.
+CONFIG_BT_MESH_PB_ADV_TRANS_PDU_RETRANSMIT_COUNT=2