[dagster-sdf] Remove docs for now-dead integration (#29129)

## Summary & Motivation

Integration being killed in
dagster-io/community-integrations#173.

As a dead integration, all docs/references should be removed (as per API
lifecycle). That said, I haven't removed the kind tags here, in case
there could be an implication for somebody still using the integration?
(Highly unlikely; I think dbt was actively migrating everybody off sdf
months ago.)

## How I Tested These Changes

BK

Author: deepyaman

docs/docs/integrations/libraries/sdf.md

@@ -88,7 +88,6 @@ RBAC
 RDS
 REST API
 SCIM
-SDF
 SFTP
 SHA
 SLA