ekf2: delete isMagBiasObservable()

src/modules/ekf2/EKF/ekf.h

@@ -859,7 +859,6 @@ private:
 	void check3DMagFusionSuitability();
 	void checkYawAngleObservability();
 	void checkMagBiasObservability();
-	bool isMagBiasObservable() const { return _mag_bias_observable; }
 	bool canUse3DMagFusion() const;
 
 	void checkMagDeclRequired();

src/modules/ekf2/EKF/mag_control.cpp

@@ -218,7 +218,7 @@ void Ekf::check3DMagFusionSuitability()
 	checkYawAngleObservability();
 	checkMagBiasObservability();
 
-	if (isMagBiasObservable() || _yaw_angle_observable) {
+	if (_mag_bias_observable || _yaw_angle_observable) {
 		_time_last_mov_3d_mag_suitable = _imu_sample_delayed.time_us;
 	}
 }