text: Title: AsyncClient.post() got an unexpected keyword argument 'proxies'
  Body: It seems that documentation for httpx does not represent fully its current code. The documentation says that ```proxies``` argument to ```AsyncClient.post()``` is available but in reality it's not:
  
  ```
  AsyncClient.post() got an unexpected keyword argument 'proxies'
  ```
  
  After removal of ```proxies``` argument from bardapi code everything works correctly.
  
  httpx 0.25.0