Remove reference to docker-ssh and docker-ssh+machine

What does this MR do?

Many years ago, with !681 (merged), we've deprecated support for docker-ssh and docker+machine-ssh executors.

With this MR we're going to entirely remove the executors from our codebase.

Why was this MR needed?

To remove already deprecated docker-ssh and docker-ssh+machine

What's the best way to test this MR?

Passing pipeline

What are the relevant issue numbers?

close #29406 (closed)