remove keyserver references from docs?

[frytg]

The docs suggest that one can use keys.openpgp.org as a keysource https://getsops.io/docs/#specify-a-different-gpg-key-server

However, this functionality seems to be removed in c6236ad

• Support for fetching keys from servers has been removed. This can be
  added back if we need to keep it around for a little longer.

Is it actually supported (it throws errors when trying it through the CLI) or is it no longer supported and should be excluded from the docs?

could be related to:
#727
#1681