AP_Arming: do not report prearm_failure_reason when ahrs unhealthy

The EKF's prearm failiure message is more related to the position estimate rather than the ahrs's health

libraries/AP_Arming/AP_Arming.cpp

@@ -144,12 +144,7 @@ bool AP_Arming::ins_checks(bool report)
         }
         if (!ahrs.healthy()) {
             if (report) {
-                const char *reason = ahrs.prearm_failure_reason();
-                if (reason) {
-                    GCS_MAVLINK::send_statustext_all(MAV_SEVERITY_CRITICAL, PSTR("PreArm: %s"), reason);
-                } else {
-                    GCS_MAVLINK::send_statustext_all(MAV_SEVERITY_CRITICAL, PSTR("PreArm: AHRS not healthy"));
-                }
+                GCS_MAVLINK::send_statustext_all(MAV_SEVERITY_CRITICAL, PSTR("PreArm: AHRS not healthy"));
             }
             return false;
         }