Mark docker-ssh and docker-ssh+machine executors as deprecated

Merged Tomasz Maczukin requested to merge deprecate-docker-ssh-executor into master

What does this MR do?

Adds deprecation notices for docker-ssh and docker-ssh+machine executors.

Does this MR meet the acceptance criteria?

  • Documentation created/updated
  • Tests
    • [-] Added for this feature/bug
    • All builds are passing
  • Branch has no merge conflicts with master (if you do - rebase it please)

What are the relevant issue numbers?

Closes #2732 (closed)