chore: slight wording improvement in README (#199)

Author: stainless-app[bot]

README.md

@@ -155,7 +155,7 @@ print(response.chat_role)
 
 ## File uploads
 
-Request parameters that correspond to file uploads can be passed as `bytes`, a [`PathLike`](https://docs.python.org/3/library/os.html#os.PathLike) instance or a tuple of `(filename, contents, media type)`.
+Request parameters that correspond to file uploads can be passed as `bytes`, or a [`PathLike`](https://docs.python.org/3/library/os.html#os.PathLike) instance or a tuple of `(filename, contents, media type)`.
 
 ```python
 from pathlib import Path