Optimize G-code flag parameters (#21849)

Marlin/src/gcode/temp/M106_M107.cpp

@@ -68,7 +68,7 @@ void GcodeSuite::M106() {
       if (t > 0) return thermalManager.set_temp_fan_speed(pfan, t);
     #endif
 
-    const uint16_t dspeed = parser.seen('A') ? thermalManager.fan_speed[active_extruder] : 255;
+    const uint16_t dspeed = parser.seen_test('A') ? thermalManager.fan_speed[active_extruder] : 255;
 
     uint16_t speed = dspeed;
 

Marlin/src/gcode/temp/M303.cpp

@@ -47,7 +47,7 @@
 void GcodeSuite::M303() {
 
   #if ANY(PID_DEBUG, PID_BED_DEBUG, PID_CHAMBER_DEBUG)
-    if (parser.seen('D')) {
+    if (parser.seen_test('D')) {
       thermalManager.pid_debug_flag ^= true;
       SERIAL_ECHO_START();
       SERIAL_ECHOPGM("PID Debug ");