[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/App/FreeCADInit.py

@@ -806,7 +806,9 @@ App.Units.Gauss         = App.Units.Quantity('G')
 
 App.Units.Weber         = App.Units.Quantity('Wb')
 
-App.Units.Oersted       = App.Units.Quantity('Oe')
+# disable Oersted because people need to input e.g. a field strength of
+# 1 ampere per meter -> 1 A/m and not get the recalculation to Oersted
+# App.Units.Oersted       = App.Units.Quantity('Oe')
 
 App.Units.PicoFarad     = App.Units.Quantity('pF')
 App.Units.NanoFarad     = App.Units.Quantity('nF')