improve error message for methods argument in HTTP method decorators

Clarify the TypeError raised when passing 'methods' to HTTP method
decorators (get, post, etc.) by indicating which decorator was used
and explicitly stating to use 'route' instead.

src/flask/sansio/scaffold.py

@@ -288,7 +288,10 @@ class Scaffold:
         options: dict[str, t.Any],
     ) -> t.Callable[[T_route], T_route]:
         if "methods" in options:
-            raise TypeError("Use the 'route' decorator to use the 'methods' argument.")
+            raise TypeError(
+                "The 'methods' argument is not allowed when using "
+                f"'{method.lower()}' decorator. Use the 'route' decorator instead."
+            )
 
         return self.route(rule, methods=[method], **options)