Remove start_watching_heater() fom M104 and M109

Marlin/Marlin_main.cpp

       if (dual_x_carriage_mode == DXC_DUPLICATION_MODE && target_extruder == 0)
         setTargetHotend1(temp == 0.0 ? 0.0 : temp + duplicate_extruder_temp_offset);
     #endif
-
-    #ifdef THERMAL_PROTECTION_HOTENDS
-      start_watching_heater(target_extruder);
-    #endif
   }
 }
 
     if (code_seen('B')) autotemp_max = code_value();
   #endif
 
-  #ifdef THERMAL_PROTECTION_HOTENDS
-    start_watching_heater(target_extruder);
-  #endif
-
   millis_t temp_ms = millis();
 
   /* See if we are heating up or cooling down */