Fix FYSETC S6 timer conflict (#20044)

Marlin/src/pins/stm32f4/pins_FYSETC_S6.h

@@ -34,8 +34,8 @@
   #define DEFAULT_MACHINE_NAME BOARD_INFO_NAME
 #endif
 
-// Change the priority to 3. Priority 2 is for software serial.
-//#define TEMP_TIMER_IRQ_PRIO                  3
+// Avoid conflict with TIMER_TONE defined in variant
+#define STEP_TIMER 10
 
 //
 // EEPROM Emulation