airspeed.msg update incorrect comments

msg/airspeed.msg

-float32 indicated_airspeed_m_s		# indicated airspeed in meters per second, -1 if unknown
-float32 true_airspeed_m_s		# true filtered airspeed in meters per second, -1 if unknown
+
+float32 indicated_airspeed_m_s		# indicated airspeed in m/s
+
+float32 true_airspeed_m_s		# true filtered airspeed in m/s
+
 float32 air_temperature_celsius		# air temperature in degrees celsius, -1000 if unknown
+
 float32 confidence			# confidence value from 0 to 1 for this sensor