jMAVSim: use PX4_SIM_SPEED_FACTOR, not cli arg

In order to be consistent between Gazebo and jMAVSim we should be using
the env variable PX4_SIM_SPEED_FACTOR in the same way. This enables
vscode to set the speed using the env variable.

Tools/jmavsim_run.sh

@@ -33,9 +33,6 @@ while getopts ":b:d:p:qsr:f:i:l" opt; do
 		r)
 			extra_args="$extra_args -r $OPTARG"
 			;;
-		f)
-			extra_args="$extra_args -f $OPTARG"
-			;;
 		l)
 			extra_args="$extra_args -lockstep"
 			;;