IDEX Improvements (#11848)

Marlin/src/gcode/feature/leds/M7219.cpp

@@ -79,7 +79,7 @@ void GcodeSuite::M7219() {
       SERIAL_ECHOPGM("led_line[");
       if (r < 10) SERIAL_CHAR(' ');
       SERIAL_ECHO(int(r));
-      SERIAL_ECHO("]=");
+      SERIAL_ECHOPGM("]=");
       for (uint8_t b = 8; b--;) SERIAL_CHAR('0' + TEST(max7219.led_line[r], b));
       SERIAL_EOL();
     }