Increase bed temperature hysteresis

Prevents heater error from bed heating too slowly.

Firmware/variants/1_75mm_MK3S-EINSy10a-E3Dv6full.h

@@ -394,7 +394,7 @@
 #endif
 
 // temperature runaway
-#define TEMP_RUNAWAY_BED_HYSTERESIS 5
+#define TEMP_RUNAWAY_BED_HYSTERESIS 15
 #define TEMP_RUNAWAY_BED_TIMEOUT 360
 
 #define TEMP_RUNAWAY_EXTRUDER_HYSTERESIS 15