fix(gdscript): Infer type from preload const

When resolving the type of the attribute from the variant, the result_type.kind was overritten for no reason.
It is assumed that this only needs to be done, if the variant value is not valid to have any kind here.

Solves #63715

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

@@ -1,3 +1,5 @@
+const A := 42
+
 func test():
 	pass