Remove old M73 / SD comment (#17928)

Marlin/src/gcode/lcd/M73.cpp

@@ -33,9 +33,6 @@
  *
  * Example:
  *   M73 P25 ; Set progress to 25%
- *
- * Notes:
- *   This has no effect during an SD print job
  */
 void GcodeSuite::M73() {
   if (parser.seen('P'))