fix: thm_gray -> thm_surface_0``

Color names were replaced with upstream names.

catppuccin_tmux.conf

@@ -6,7 +6,7 @@ set status-right-length "100"
 
 %if "#{==:#{@catppuccin_status_background},default}"
   set -gF status-style "bg=#{@thm_bg},fg=#{@thm_fg}"
-  set -gF @message_background "#{@thm_gray}"
+  set -gF @message_background "#{@thm_surface_0}"
 %elif "#{==:#{@catppuccin_status_background},none}"
   set -g status-style "default"
   set -g @message_background "default"