[FEM] Elmer: don't push mesh scaled to Elmer

- the mesh scaling was a hack to work around the fact that FC's mesh is in mm while all input units are in SI. It turned out that this made more problems than it solved because Elmer checks the length unit and makes internal recalculations. So the mesh must not be scaled when send to Elmer (despite the ElmerGrid docs doesn't state this).
forum thread: https://forum.freecadweb.org/viewtopic.php?p=614162#p614162

src/Mod/Fem/femsolver/elmer/tasks.py

@@ -252,7 +252,6 @@ class Results(run.Results):
             self.fail()
             return
         self.solver.ElmerResult.read(postPath)
-        self.solver.ElmerResult.scale(1000)
         self.solver.ElmerResult.getLastPostObject().touch()
         self.solver.Document.recompute()
 

src/Mod/Fem/femsolver/elmer/writer.py

@@ -224,8 +224,7 @@ class Writer(object):
             argsBasic = [binary,
                          _ELMERGRID_IFORMAT,
                          _ELMERGRID_OFORMAT,
-                         unvPath,
-                         "-scale", "0.001", "0.001", "0.001"]
+                         unvPath]
             args = argsBasic
             args.extend(["-out", self.directory])
             if system() == "Windows":