Fix SKR E3 DIP pin CLCD_SPI_CS (#20078)

Marlin/src/pins/stm32f1/pins_BTT_SKR_E3_DIP.h

   #define BEEPER_PIN                        PB6
 
   #define CLCD_MOD_RESET                    PA9
-  #define CLCD_SPI_CS                       PA8
+  #define CLCD_SPI_CS                       PB8
 
 #endif // TOUCH_UI_FTDI_EVE && LCD_FYSETC_TFT81050