Websockets need to be above version 13

At version 11 (as indicated in meta.yaml it fails)
```
from websockets.asyncio.client import ClientConnection, connect
ModuleNotFoundError: No module named 'websockets.asyncio
```

https://github.com/conda-forge/prefect-feedstock/blob/44fffff98f7e927a4a7029e0bf64f96bc22e63ad/recipe/meta.yaml#L82
