Fix Python 3.14 annotations AttributeError

PiperOrigin-RevId: 883406805

Author: AleksMat

infra/base-images/base-builder/indexer/manifest_types.py

@@ -24,6 +24,7 @@
 
 import dataclasses
 import enum
+import inspect
 import io
 import json
 import logging
@@ -379,7 +380,7 @@ def validate(self) -> None:
               " empty URL. Source map entry: {ref}"
           )
     # check very simple basic types.
-    for k, v in self.__annotations__.items():
+    for k, v in inspect.get_annotations(type(self)).items():
       if not isinstance(v, type):
         continue
       if not isinstance(getattr(self, k), v):