AP_RangeFinder: param desc rename from PX4-PWM to just PWM

the PWM driver is available for many boards

libraries/AP_RangeFinder/AP_RangeFinder_Params.cpp

@@ -6,7 +6,7 @@ const AP_Param::GroupInfo AP_RangeFinder_Params::var_info[] = {
     // @Param: TYPE
     // @DisplayName: Rangefinder type
     // @Description: What type of rangefinder device that is connected
-    // @Values: 0:None,1:Analog,2:MaxbotixI2C,3:LidarLiteV2-I2C,5:PX4-PWM,6:BBB-PRU,7:LightWareI2C,8:LightWareSerial,9:Bebop,10:MAVLink,11:uLanding,12:LeddarOne,13:MaxbotixSerial,14:TeraRangerI2C,15:LidarLiteV3-I2C,16:VL53L0X,17:NMEA,18:WASP-LRF,19:BenewakeTF02,20:BenewakeTFmini,21:LidarLightV3HP,22:PWM,23:BlueRoboticsPing,24:UAVCAN,25:BenewakeTFMiniPlus
+    // @Values: 0:None,1:Analog,2:MaxbotixI2C,3:LidarLiteV2-I2C,5:PWM,6:BBB-PRU,7:LightWareI2C,8:LightWareSerial,9:Bebop,10:MAVLink,11:uLanding,12:LeddarOne,13:MaxbotixSerial,14:TeraRangerI2C,15:LidarLiteV3-I2C,16:VL53L0X,17:NMEA,18:WASP-LRF,19:BenewakeTF02,20:BenewakeTFmini,21:LidarLightV3HP,22:PWM,23:BlueRoboticsPing,24:UAVCAN,25:BenewakeTFMiniPlus
     // @User: Standard
     AP_GROUPINFO("TYPE",    1, AP_RangeFinder_Params, type, 0),