Fix error next command in autotune (PR#2274)

Now send only temperature for T or B, but not send OK.
Host interprets the line to show the right temperature, but not in
response to M105 then stop and send commands until it ends the autotune.

Marlin/Marlin_main.cpp

@@ -4510,9 +4510,6 @@ inline void gcode_M303() {
   int c = code_seen('C') ? code_value_short() : 5;
   float temp = code_seen('S') ? code_value() : (e < 0 ? 70.0 : 150.0);
   PID_autotune(temp, e, c);
-  // Suppress a line mismatch error
-  gcode_LastN += 1;
-  FlushSerialRequestResend();
 }
 
 #ifdef SCARA