completion: ACME plugin type: comment out http type for now, not useful

completion: ACME plugin type: comment out http type for now, not useful

It may make sense in the future, e.g., if the built-in standalone
type is not enough, e.g., as HTTP**s**, HTTP 2 or even QUIC (HTTP 3)
is wanted in some setups, but for now there's no scenario where one
would profit from adding a new HTTP plugin, especially as it requires
the `data` property to be set, which makes no sense..

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>