Pins httpx version to 0.20.0 till it releases 1.0 stable release.
There is an incompatible change, that the redirects are not followed by default.
This is because of the change in default in httpx itself. To follow redirects by default,
pass `follow_redirects=True` in `webdav4.fsspec.WebdavFileSystem` or in `webdav4.client.Client`.
If you cannot change the API for some reason, you can set `FSSPEC_DAV_FOLLOW_REDIRECTS=true` or
override through fsspec's config.