Update docs/executors/README.md

This is a general Merge Request template. Consider to choose a template from the list above if it will match your case more.

What does this MR do?

Update docs/executors/README.md

• Reordered table columns to show executors from the least featured (SSH) to the most complete (Kubernetes)
• Replaced "no" with unicode X mark on tables

Why was this MR needed?

This change helps to better compare executors because it orders them from the least to the most complete

Are there points in the code the reviewer needs to double check?

Nope, the changes were only to reorder columns on tables

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?

No issue numbers here