Use pgm_read_ptr for tables of pointers

Marlin/Marlin_main.cpp

@@ -8138,7 +8138,7 @@ inline void gcode_M111() {
     for (uint8_t i = 0; i < COUNT(debug_strings); i++) {
       if (TEST(marlin_debug_flags, i)) {
         if (comma++) SERIAL_CHAR(',');
-        serialprintPGM((char*)pgm_read_word(&debug_strings[i]));
+        serialprintPGM((char*)pgm_read_ptr(&debug_strings[i]));
       }
     }
   }