chore: change submenu "quit" to "back"

Changing the "Quit" option to "Back" as it is more intuitive, causes less confusion and is in fact the more fitting description of what is happening.

scripts/ui/update_menu.sh

@@ -24,7 +24,7 @@ update_ui(){
   echo -e "|  8) [PrettyGCode]      |  $LOCAL_PGC_COMMIT | $REMOTE_PGC_COMMIT | "
   echo -e "|                        |------------------------------| "
   echo -e "|  9) [System]           |  $DISPLAY_SYS_UPDATE   | "
-  quit_footer
+  back_footer
 }
 
 update_menu(){
@@ -55,7 +55,7 @@ update_menu(){
         do_action "update_system" "update_ui";;
       a)
         do_action "update_all" "update_ui";;
-      Q|q)
+      B|b)
         clear; main_menu; break;;
       *)
         deny_action "update_ui";;