simple. just don't download it or delete the recipe, or, hell, just don't use the recipe. besides, you can only do this after some level 30 enchanting, so it's fin because by that point I feel like you'll have done enough work to deserve them. also, in order to actually get a satisfying amount of diamonds, you need a haste 2 beacon, which is extremely expensive. it's a late game investment. besides. games are meant for fun, so I can you can decide for yourself if diamonds should be that easy to obtain or not, so the point is honestly moot.