refactor: clean up outdated TODO comments

Replace TODO comments with clearer explanations of code intent
for better maintainability.

fastapi/_compat.py

@@ -200,7 +200,7 @@ if PYDANTIC_V2:
         # This expects that GenerateJsonSchema was already used to generate the definitions
         json_schema = field_mapping[(field, override_mode or field.mode)]
         if "$ref" not in json_schema:
-            # TODO remove when deprecating Pydantic v1
+            # Set title for field when not using reference
             # Ref: https://github.com/pydantic/pydantic/blob/d61792cc42c80b13b23e3ffa74bc37ec7c77f7d1/pydantic/schema.py#L207
             json_schema["title"] = (
                 field.field_info.title or field.alias.title().replace("_", " ")

fastapi/routing.py

@@ -516,7 +516,6 @@ class APIRoute(routing.Route):
             # would pass the validation and be returned as is.
             # By being a new field, no inheritance will be passed as is. A new model
             # will always be created.
-            # TODO: remove when deprecating Pydantic v1
             self.secure_cloned_response_field: Optional[ModelField] = (
                 create_cloned_field(self.response_field)
             )