[fleche] Remove FailedPermanent 8.16 hack

This was not nice, and not needed anymore.

fleche/theory.ml

@@ -223,7 +223,7 @@ end = struct
       Option.bind !hint (fun (uri, (l, c)) ->
           if Lang.LUri.File.equal uri doc.uri then
             match doc.completed with
-            | Yes _ | Failed _ | FailedPermanent _ -> None
+            | Yes _ | Failed _ -> None
             | Stopped range when Doc.Target.reached ~range (l, c) -> None
             | Stopped _ -> Some (Doc.Target.Position (l, c))
           else None)