[Core] disable the the unit Oersted

- is not feasible for practical usage and (was up to now not used, thus no consequence)
  moreover, Oersted is a cgs unit while we use SI units, thus also not suitable for FEM, only makes problems for magnetization

src/Base/UnitsSchemaMKS.cpp

@@ -300,8 +300,8 @@ QString UnitsSchemaMKS::schemaTranslate(const Quantity &quant, double &factor, Q
         }
     }
     else if (unit == Unit::MagneticFieldStrength) {
-        unitString = QString::fromLatin1("Oe");
-        factor = 0.07957747;
+        unitString = QString::fromLatin1("A/m");
+        factor = 1e-3;
     }
     else if (unit == Unit::MagneticFlux) {
         unitString = QString::fromLatin1("Wb");