Update instructions to make subresources unique in inspector (#3895)

As of 3.2.2 the icon for Object Properties is no longer a down arrow, it is now a tools emoji. It's also not clear from the sentence the tutorial is expecting the user to look for the Object Properties button, just 'the down arrow', so I added clarity there as well.

getting_started/step_by_step/instancing.rst

@@ -102,8 +102,9 @@ changes to that scene will affect all instances.
 You can also adjust individual instances. Set the bounce value back to ``0``
 and then in the ``Main`` scene, select one of the instanced balls. Resources
 like ``PhysicsMaterial`` are shared between instances by default, so we need
-to make it unique. Click on the down arrow and select "Make Unique". Set its
-``Bounce`` to ``1`` and press "Play".
+to make it unique. Click on the tools button in the top-right of the Inspector
+dock and select "Make Sub-Resources Unique". Set its ``Bounce`` to ``1`` and
+press "Play".
 
 .. image:: img/instancing_property.png