GDScript: Fix test from #69163 after annotations change

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

@@ -11,7 +11,7 @@ func param_inferred(param := variant()) -> void: print(param)
 func return_untyped(): return variant()
 func return_typed() -> Variant: return variant()
 
-@warning_ignore(unused_variable)
+@warning_ignore("unused_variable")
 func test() -> void:
 	var weak = variant()
 	var typed: Variant = variant()