Fix the totw MA attack book droprates

After about 10 full clears of ToTW,<<<
i’ve gotten something like:

10-15x Tattered book: Sting of the Viper (section 5)
10-15x Tattered book: Stampede of the Boar (section 5)

Often same run gives multple section 5’s and I’ve even seen 2x same ones
on one corpse. I believe the problem is all bosses having a chance to drop chapter 5,
which seems pretty big. But the other sections are extremely rare and I’ve not seen
a single one

I wouldn’t mind farming more if I actually saw the other sections sometimes.

please fix