Cost model miscalculates the degree of lookup arguments

[daira]

halo2/halo2_proofs/examples/cost-model.rs

Lines 127 to 129 in 95df0af

	fn required_degree(&self) -> usize {
	1 + cmp::max(1, self.input_deg) + cmp::max(1, self.table_deg)
	}

does not match

halo2/halo2_proofs/src/plonk/lookup.rs

Lines 65 to 70 in 95df0af

	std::cmp::max(
	// (1 - (l_last + l_blind)) z(\omega X) (a'(X) + \beta) (s'(X) + \gamma)
	4,
	// (1 - (l_last + l_blind)) z(X) (\theta^{m-1} a_0(X) + ... + a_{m-1}(X) + \beta) (\theta^{m-1} s_0(X) + ... + s_{m-1}(X) + \gamma)
	2 + input_degree + table_degree,
	)