Fix IntrospectionQuery type definition (#234)

Author: sobolevn

src/graphql/utilities/get_introspection_query.py

@@ -302,7 +302,8 @@ class IntrospectionSchema(MaybeWithDescription):
     directives: list[IntrospectionDirective]
 
 
-class IntrospectionQuery(TypedDict):
-    """The root typed dictionary for schema introspections."""
-
-    __schema: IntrospectionSchema
+# The root typed dictionary for schema introspections.
+IntrospectionQuery = TypedDict(  # noqa: UP013
+    "IntrospectionQuery",
+    {"__schema": IntrospectionSchema},
+)