GDScript: Fix inheritance check of @onready for inner classes

modules/gdscript/tests/scripts/analyzer/features/onready_on_inner_class_with_non_node_outer.gd

@@ -0,0 +1,7 @@
+extends RefCounted
+
+func test():
+	print("ok")
+
+class Inner extends Node:
+	@onready var okay = 0

modules/gdscript/tests/scripts/analyzer/features/onready_on_inner_class_with_non_node_outer.out

@@ -0,0 +1,2 @@
+GDTEST_OK
+ok