Potentially resolved issue in contributors guide

[patrick-motard]

@nicm The contributing guide mentions #3114 as a good beginner issue. From my testing it looks like this issue is fixed.

Steps used:

  # Start tmux with no config and multiple status lines
  ./tmux -L test -f /dev/null new-session

  # Inside tmux, run these commands (prefix is Ctrl+b, then :)

  # Set 3 status lines
  # Ctrl+b : set -g status 3

  # Set message-line to 2 (third line, 0-indexed)
  # Ctrl+b : set -g message-line 2

  # Now trigger a message or command prompt:
  # Ctrl+b : display-message "Test message"

  # Or open the command prompt:
  # Ctrl+b :

  # Observe which status line the message/prompt appears on
  # It should appear on line 2 (the third status line from top of status block)

  # Try changing it:
  # Ctrl+b : set -g message-line 0
  # Ctrl+b : display-message "Now on line 0"

[nicm]

Yes, I have removed it, thanks.