[3.x] Fix `NodePath` subname index range documentation

doc/classes/NodePath.xml

@@ -96,7 +96,7 @@
 			<return type="String" />
 			<argument index="0" name="idx" type="int" />
 			<description>
-				Gets the resource or property name indicated by [code]idx[/code] (0 to [method get_subname_count]).
+				Gets the resource or property name indicated by [code]idx[/code] (0 to [method get_subname_count] - 1).
 				[codeblock]
 				var node_path = NodePath("Path2D/PathFollow2D/Sprite:texture:load_path")
 				print(node_path.get_subname(0)) # texture