Remove unnecessary re-adding of extruders

This was originally added for backwards compatibility with old versions of Uranium. However the link between Cura versions and Uranium versions is already very strong (Cura crashes with old Uranium versions) so this is not necessary.
It was also adding warnings in our log that these extruders had already been added to the printer.

Done during Turbo Testing and Tooling, to clean up our log files.

cura/Settings/ExtruderManager.py

@@ -143,25 +143,6 @@ class ExtruderManager(QObject):
                     return self._extruder_trains[global_container_stack.getId()][str(index)]
         return None
 
-    def registerExtruder(self, extruder_train: "ExtruderStack", machine_id: str) -> None:
-        changed = False
-
-        if machine_id not in self._extruder_trains:
-            self._extruder_trains[machine_id] = {}
-            changed = True
-
-        # do not register if an extruder has already been registered at the position on this machine
-        if any(item.getId() == extruder_train.getId() for item in self._extruder_trains[machine_id].values()):
-            Logger.log("w", "Extruder [%s] has already been registered on machine [%s], not doing anything",
-                       extruder_train.getId(), machine_id)
-            return
-
-        if extruder_train:
-            self._extruder_trains[machine_id][extruder_train.getMetaDataEntry("position")] = extruder_train
-            changed = True
-        if changed:
-            self.extrudersChanged.emit(machine_id)
-
     ##  Gets a property of a setting for all extruders.
     #
     #   \param setting_key  \type{str} The setting to get the property of.

cura/Settings/ExtruderStack.py

@@ -44,9 +44,6 @@ class ExtruderStack(CuraContainerStack):
         stack.addExtruder(self)
         self.setMetaDataEntry("machine", stack.id)
 
-        # For backward compatibility: Register the extruder with the Extruder Manager
-        ExtruderManager.getInstance().registerExtruder(self, stack.id)
-
     @override(ContainerStack)
     def getNextStack(self) -> Optional["GlobalStack"]:
         return super().getNextStack()

tests/TestExtruderManager.py

@@ -15,17 +15,3 @@ def test_getAllExtruderSettings(extruder_manager):
     extruder_2.getProperty = MagicMock(return_value="zomg")
     extruder_manager.getActiveExtruderStacks = MagicMock(return_value = [extruder_1, extruder_2])
     assert extruder_manager.getAllExtruderSettings("whatever", "value") == ["beep", "zomg"]
-
-
-def test_registerExtruder(extruder_manager):
-    extruder = createMockedExtruder("beep")
-    extruder.getMetaDataEntry = MagicMock(return_value = "0")  # because the extruder position gets called
-
-    extruder_manager.extrudersChanged = MagicMock()
-    extruder_manager.registerExtruder(extruder, "zomg")
-
-    assert extruder_manager.extrudersChanged.emit.call_count == 1
-
-    # Doing it again should not trigger anything
-    extruder_manager.registerExtruder(extruder, "zomg")
-    assert extruder_manager.extrudersChanged.emit.call_count == 1