Enable M191 (#15531)

Marlin/src/gcode/gcode.cpp

 
       #if HAS_HEATED_CHAMBER
         case 141: M141(); break;                                  // M141: Set chamber temperature
-        //case 191: M191(); break;                                // M191: Wait for chamber temperature to reach target
+        case 191: M191(); break;                                  // M191: Wait for chamber temperature to reach target
       #endif
 
       #if ENABLED(AUTO_REPORT_TEMPERATURES) && HAS_TEMP_SENSOR

Marlin/src/gcode/gcode.h

 
   #if HAS_HEATED_CHAMBER
     static void M141();
-    //static void M191();
+    static void M191();
   #endif
 
   #if HOTENDS && HAS_LCD_MENU

Marlin/src/gcode/temperature/M141_M191.cpp

 #include "../gcode.h"
 #include "../../module/temperature.h"
 
-/*
 #include "../../module/motion.h"
 #include "../../lcd/ultralcd.h"
 
 #endif
 
 #include "../../Marlin.h" // for wait_for_heatup and idle()
-*/
 
 /**
  * M141: Set chamber temperature
  * M191: Sxxx Wait for chamber current temp to reach target temp. Waits only when heating
  *       Rxxx Wait for chamber current temp to reach target temp. Waits when heating and cooling
  */
-/*
 void GcodeSuite::M191() {
   if (DEBUGGING(DRYRUN)) return;
 
   }
   else return;
 
-  lcd_setstatusPGM(thermalManager.isHeatingChamber() ? GET_TEXT(MSG_CHAMBER_HEATING) : GET_TEXT(MSG_CHAMBER_COOLING));
-
-  thermalManager.wait_for_chamber(no_wait_for_cooling);
+  const bool is_heating = thermalManager.isHeatingChamber();
+  if (is_heating || !no_wait_for_cooling) {
+    lcd_setstatusPGM(is_heating ? GET_TEXT(MSG_CHAMBER_HEATING) : GET_TEXT(MSG_CHAMBER_COOLING));
+    thermalManager.wait_for_chamber(false);
+  }
 }
-*/
 
 #endif // HAS_HEATED_CHAMBER

Marlin/src/module/temperature.cpp

 
   #endif // HAS_HEATED_BED
 
-  #if 0 && HAS_HEATED_CHAMBER
+  #if HAS_HEATED_CHAMBER
 
     #ifndef MIN_COOLING_SLOPE_DEG_CHAMBER
       #define MIN_COOLING_SLOPE_DEG_CHAMBER 1.50