Don't reset selected material upon container changed

The onActiveMaterialChanged signal is triggered upon loading a material for the first time. This is hard to fix without breaking stuff, so we will revert this part.

This re-introduces a bug where if you change a material diameter such that the material disappears from the list, it is still selected and you can change its properties in the details panel.

Contributes to issue CURA-6679.

resources/qml/Preferences/Materials/MaterialsPage.qml

@@ -48,15 +48,6 @@ Item
     // When loaded, try to select the active material in the tree
     Component.onCompleted: resetExpandedActiveMaterial()
 
-    Connections
-    {
-        target: Cura.MachineManager
-        onActiveMaterialChanged:
-        {
-            resetExpandedActiveMaterial()
-        }
-    }
-
     // Every time the selected item has changed, notify to the details panel
     onCurrentItemChanged:
     {