tests: bsim: BT LL throughput: Increase execution timeout

To avoid these test from timing out in slow CI runners let's increase
their timeout.
This does not affect the test themselves in any way.
This timeout is a watchdog that kills the test in case it hangs.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>

tests/bsim/bluetooth/ll/throughput/tests_scripts/gatt_write.sh

diff --git a/tests/bsim/bluetooth/ll/throughput/tests_scripts/gatt_write.sh b/tests/bsim/bluetooth/ll/throughput/tests_scripts/gatt_write.sh
index 32f4fed..97b487f 100755
--- a/tests/bsim/bluetooth/ll/throughput/tests_scripts/gatt_write.sh
+++ b/tests/bsim/bluetooth/ll/throughput/tests_scripts/gatt_write.sh
@@ -7,7 +7,7 @@
 
 simulation_id="ll-throughput"
 verbosity_level=2
-EXECUTE_TIMEOUT=180
+EXECUTE_TIMEOUT=300
 
 cd ${BSIM_OUT_PATH}/bin