Fix compile warning comparison uint and int (#12788)

Marlin/src/gcode/temperature/M106_M107.cpp

@@ -51,7 +51,7 @@ void GcodeSuite::M106() {
 
   if (p < MIN(EXTRUDERS, FAN_COUNT)) {
     uint16_t s = parser.ushortval('S', 255);
-    NOMORE(s, 255);
+    NOMORE(s, 255U);
 
     uint8_t np = p;