Removed SDSLOW for ELB_FULL_GRAPHIC_CONTROLLER

Hardware changes has removed the need for this option.

Marlin/Conditionals.h

       #ifdef ELB_FULL_GRAPHIC_CONTROLLER_SDCARDDETECTINVERTED
         #define SDCARDDETECTINVERTED
       #endif
-      #define SDSLOW
       #define U8GLIB_LM6059_AF
     #endif