AP_GPS: allow GPS moving baseline rover at 3Hz

users with busy CAN bus often get significiantly lower GPS rates on a
moving baseline rover, preventing arming. This PR relaxes the required
frame rate as the EKF is quite happy with 3Hz yaw and the yaw is the
only data consumed from a moving baseline rover

libraries/AP_GPS/AP_GPS.cpp

@@ -2065,12 +2065,14 @@ bool AP_GPS::is_healthy(uint8_t instance) const
 #else
     /*
       allow two lost frames before declaring the GPS unhealthy, but
-      require the average frame rate to be close to 5Hz. We allow for
-      a bit higher average for a rover due to the packet loss that
-      happens with the RTCMv3 data
+      require the average frame rate to be close to 5Hz.
+
+      We allow for a rate of 3Hz average for a moving baseline rover
+      due to the packet loss that happens with the RTCMv3 data and the
+      fact that the rate of yaw data is not critical
      */
     const uint8_t delay_threshold = 2;
-    const float delay_avg_max = ((_type[instance] == GPS_TYPE_UBLOX_RTK_ROVER) || (_type[instance] == GPS_TYPE_UAVCAN_RTK_ROVER))?245:215;
+    const float delay_avg_max = ((_type[instance] == GPS_TYPE_UBLOX_RTK_ROVER) || (_type[instance] == GPS_TYPE_UAVCAN_RTK_ROVER))?333:215;
     const GPS_timing &t = timing[instance];
     bool delay_ok = (t.delayed_count < delay_threshold) &&
         t.average_delta_ms < delay_avg_max &&