Update Optional[x] -> x | None and Union[x, y] to x | y (#26633)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

tests/distributed/test_pipeline_parallel.py

@@ -11,7 +11,7 @@ WARNING: This test runs in both single-node (4 GPUs) and multi-node
 import json
 import os
 from dataclasses import dataclass
-from typing import Literal, NamedTuple, Optional
+from typing import Literal, NamedTuple
 
 import pytest
 
@@ -35,7 +35,7 @@ class ParallelSetup(NamedTuple):
 
 class PPTestOptions(NamedTuple):
     multi_node_only: bool
-    load_format: Optional[str] = None
+    load_format: str | None = None
 
 
 @dataclass
@@ -52,7 +52,7 @@ class PPTestSettings:
         pp_base: int = 2,
         multi_node_only: bool = False,
         runner: RunnerOption = "auto",
-        load_format: Optional[str] = None,
+        load_format: str | None = None,
     ):
         return PPTestSettings(
             parallel_setups=[
@@ -76,7 +76,7 @@ class PPTestSettings:
         pp_base: int = 2,
         runner: RunnerOption = "auto",
         multi_node_only: bool = False,
-        load_format: Optional[str] = None,
+        load_format: str | None = None,
     ):
         return PPTestSettings(
             parallel_setups=[