Fixes for https://github.com/acts-project/acts/pull/3983

Tracking/Acts/ActsGeometry/ActsGeometry/ATLASMagneticFieldWrapper.h

@@ -54,34 +54,6 @@ public:
     return Acts::Result<Acts::Vector3>::success(bfield);
   }
 
-  Acts::Result<Acts::Vector3>
-  getFieldGradient(const Acts::Vector3& position,
-                   Acts::ActsMatrix<3, 3>& gradient,
-                   Acts::MagneticFieldProvider::Cache& gcache) const override
-  {
-    Cache& cache = gcache.as<Cache>();
-    double posXYZ[3];
-    posXYZ[0] = position.x();
-    posXYZ[1] = position.y();
-    posXYZ[2] = position.z();
-    double BField[3];
-    double grad[9];
-
-    cache.fieldCache.getField(posXYZ, BField, grad);
-
-    // Magnetic field
-    Acts::Vector3 bfield{BField[0], BField[1],BField[2]};
-    Acts::ActsMatrix<3, 3> tempGrad;
-    tempGrad << grad[0], grad[1], grad[2], grad[3], grad[4], grad[5], grad[6], grad[7], grad[8]; 
-    gradient = tempGrad;
-
-
-    bfield *= m_bFieldUnit; // kT -> T;
-    gradient *= m_bFieldUnit;
-
-    return Acts::Result<Acts::Vector3>::success(bfield);
-  }
-
 private:
   const double m_bFieldUnit = 1000.*Acts::UnitConstants::T;
 };