Update resources.rst to make inner class note more clear

The term "subclass" is often used as a synonym for "child class", so using it here to refer to an inner class is just confusing, even with the "i.e. an inner class" part. The GDScript Reference page simply uses the term "inner class" and never refers to them as "subclass", so this is also consistent with that.

tutorials/scripting/resources.rst

@@ -362,9 +362,9 @@ Now, select the :ref:`CharacterBody3D <class_CharacterBody3D>` node which we nam
 
     Beware that resource files (\*.tres/\*.res) will store the path of the script
     they use in the file. When loaded, they will fetch and load this script as an
-    extension of their type. This means that trying to assign a subclass, i.e. an
-    inner class of a script (such as using the ``class`` keyword in GDScript) won't
-    work. Godot will not serialize the custom properties on the script subclass properly.
+    extension of their type. This means that trying to assign an
+    inner class of a script (i.e. using the ``class`` keyword in GDScript) won't
+    work. Godot will not serialize the custom properties on the script inner class properly.
 
     In the example below, Godot would load the ``Node`` script, see that it doesn't
     extend ``Resource``, and then determine that the script failed to load for the