Fix odom callback and behaviours launch file

[lopetit]

The odom callback at

racecar/racecar_behaviors/racecar_behaviors/path_following.py

Lines 36 to 37 in 26a61e6

	def odom_callback(self, msg):
	self.get_logger().info('Current speed: %f' % msg.twist.twist.linear.x)

is not entered, probably because of the topic names in the launch file

racecar/racecar_behaviors/launch/behaviors.launch.py

Line 23 in 26a61e6

(f"/{prefix}/odom", f"/{prefix}/odometry/filtered"),