py-anyio: updated to 3.3.0

3.3.0

Added asynchronous Path class
Added the wrap_file() function for wrapping existing files as asynchronous file objects
Relaxed the type of the path initializer argument to FileReadStream and FileWriteStream so they accept any path-like object (including the new asynchronous Path class)
Dropped unnecessary dependency on the async_generator library
Changed the generics in AsyncFile so that the methods correctly return either str or bytes based on the argument to open_file()
Fixed an asyncio bug where under certain circumstances, a stopping worker thread would still accept new assignments, leading to a hang

(adam)