refactor: remove ovh_vrack_dedicated_server

[Arnoways]

From the testing I did, using "ovh_vrack_dedicated_server" through terraform did not work. I tried using the API calls directly without sucess, hence this commit:

Removing this resource as the API call it executes is tagged as "LEGACY" in ovh's API and does not work anymore. We should favor ovh_vrack_dedicated_server_interface which calls functional routes and avoids confusion. I also updated the example for this resource to be more dynamic so the user will know they won't have to manually search for their interfaces' IDs.

Signed-off-by: Arnaud SINAYS [email protected]