Standardized max temp values

Everywhere in menu items temperatures are "defined value" subtracted by 15.
In one place is subtracted by 5

Marlin/src/lcd/ultralcd.cpp

@@ -2052,7 +2052,7 @@ void kill_screen(const char* lcd_msg) {
       MENU_BACK(MSG_UBL_BUILD_MESH_MENU);
       MENU_ITEM_EDIT(int3, MSG_UBL_CUSTOM_HOTEND_TEMP, &custom_hotend_temp, EXTRUDE_MINTEMP, (HEATER_0_MAXTEMP - 10));
       #if HAS_TEMP_BED
-        MENU_ITEM_EDIT(int3, MSG_UBL_CUSTOM_BED_TEMP, &custom_bed_temp, BED_MINTEMP, (BED_MAXTEMP - 5));
+        MENU_ITEM_EDIT(int3, MSG_UBL_CUSTOM_BED_TEMP, &custom_bed_temp, BED_MINTEMP, (BED_MAXTEMP - 15));
       #endif
       MENU_ITEM(function, MSG_UBL_BUILD_CUSTOM_MESH, _lcd_ubl_build_custom_mesh);
       END_MENU();