feat(client): allow passing NotGiven for body (#2135)

fix(client): mark some request bodies as optional

src/openai/_base_client.py

@@ -520,7 +520,7 @@ def _build_request(
             # so that passing a `TypedDict` doesn't cause an error.
             # https://github.com/microsoft/pyright/issues/3526#event-6715453066
             params=self.qs.stringify(cast(Mapping[str, Any], params)) if params else None,
-            json=json_data,
+            json=json_data if is_given(json_data) else None,
             files=files,
             **kwargs,
         )