[cfr_json_colab] Remove the use of typing.Self.

Sadly, typing.Self is a Python 3.11 feature, and public Colab runtimes are
stuck at 3.10. Other uses are not reachable from our Colab, and thus do not
need to be changed.

python/gmpro/two_step_routing/_parking.py

@@ -23,7 +23,7 @@
 import copy
 import dataclasses
 import functools
-from typing import Any, Self, TypeAlias
+from typing import Any, TypeAlias
 
 from ..json import cfr_json
 
@@ -106,7 +106,7 @@ class InitialLocalModelGrouping:
   )
 
   @classmethod
-  def from_string(cls, options: str) -> Self:
+  def from_string(cls, options: str) -> "InitialLocalModelGrouping":
     """Creates the grouping specification from command-line flags.
 
     Args: