Update poseidon.md - Filecoin spec has a minor typo

[flipdazed]

There’s a minor error in filecoin paper

calc_round_numbers(p,M,t,α) is a typo… It does not receive alpha as final parameters it receives $c_{\alpha} \in {0, 1, 2}$

As per the source code

if sbox_case == 0:
    print "S-box: f(x) = x^3"
elif sbox_case == 1:
    print "S-box: f(x) = x^5"
elif sbox_case == 2:
    print "S-box: f(x) = x^(-1)"

It’s quite obvious so idk if anyone cares - maybe it was updated since the spec was written...?