Refactor typing for grant_types in auth.py

Author: automaton82

src/mcp/shared/auth.py

@@ -1,4 +1,4 @@
-from typing import Any, Literal, Union
+from typing import Any, Literal
 
 from pydantic import AnyHttpUrl, AnyUrl, BaseModel, Field, field_validator
 
@@ -47,7 +47,7 @@ class OAuthClientMetadata(BaseModel):
     # ie: we do not support client_secret_basic
     token_endpoint_auth_method: Literal["none", "client_secret_post"] = "client_secret_post"
     # grant_types: this implementation only supports authorization_code & refresh_token
-    grant_types: list[Union[Literal["authorization_code", "refresh_token"], str]] = [
+    grant_types: list[Literal["authorization_code", "refresh_token"] | str] = [
         "authorization_code",
         "refresh_token",
     ]