Merge pull request #2136 from thinkyhead/M303_suppress_error

Suppress the line mismatch error after M303

Marlin/Marlin_main.cpp

   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