Add option to enable/disable autoretract altogether (#11904)

Marlin/src/gcode/gcode.cpp

@@ -474,9 +474,11 @@ void GcodeSuite::process_parsed_command(
       #if ENABLED(FWRETRACT)
         case 207: M207(); break;                                  // M207: Set Retract Length, Feedrate, and Z lift
         case 208: M208(); break;                                  // M208: Set Recover (unretract) Additional Length and Feedrate
-        case 209:
-          if (MIN_AUTORETRACT <= MAX_AUTORETRACT) M209();         // M209: Turn Automatic Retract Detection on/off
-          break;
+        #if ENABLED(FWRETRACT_AUTORETRACT)
+          case 209:
+            if (MIN_AUTORETRACT <= MAX_AUTORETRACT) M209();       // M209: Turn Automatic Retract Detection on/off
+            break;
+        #endif
       #endif
 
       case 211: M211(); break;                                    // M211: Enable, Disable, and/or Report software endstops