Revert "Swap alt-{left,right,backspace,delete} with ctrl-* on macOS"

This reverts commit ebdc3a0393.

Not discussed, includes a new thing that queries the terminal for the client OS
when what is really needed is just a `uname` - which would also work on Terminal.app.

share/functions/__fish_config_interactive.fish

@@ -217,13 +217,6 @@ end" >$__fish_config_dir/config.fish
     end
     __fish_update_cwd_osc # Run once because we might have already inherited a PWD from an old tab
 
-    if set -q TMUX
-        # NOTE This will be stale when the next tmux client attaches to fish's window.
-        # This isn't oo bad since we only use this to detect the client OS.
-        # TODO we should have a client scope.
-        set -g __fish_tmux_client_tty (tmux display-message -p '#{client_tty}' 2>/dev/null)
-    end
-
     # Bump this whenever some code below needs to run once when upgrading to a new version.
     # The universal variable __fish_initialized is initialized in share/config.fish.
     set __fish_initialized 3800