chore: enable pyupgrade fixes

Schema reflection code needed a minor adjustment to handle UnionTypes
and collections.abc.AsyncIterator. (Both are preferred for latest Python
releases.)

Signed-off-by: Ihar Hrachyshka <ihar.hrachyshka@gmail.com>

llama_stack/distribution/ui/modules/api.py

@@ -5,7 +5,6 @@
 # the root directory of this source tree.
 
 import os
-from typing import Optional
 
 from llama_stack_client import LlamaStackClient
 
@@ -23,7 +22,7 @@ class LlamaStackApi:
             },
         )
 
-    def run_scoring(self, row, scoring_function_ids: list[str], scoring_params: Optional[dict]):
+    def run_scoring(self, row, scoring_function_ids: list[str], scoring_params: dict | None):
         """Run scoring on a single row"""
         if not scoring_params:
             scoring_params = {fn_id: None for fn_id in scoring_function_ids}