Fix ranked voting math comment

[nuke-web3]

Unless I am misunderstanding, the comments are suggesting incorrect values:

substrate/frame/ranked-collective/src/lib.rs

Lines 199 to 228 in badc92a

	/// Vote-weight scheme where all voters get one vote plus an additional vote for every excess rank
	/// they have. I.e.:
	///
	/// - Each member with no excess rank gets 1 vote;
	/// - ...with an excess rank of 1 gets 2 votes;
	/// - ...with an excess rank of 2 gets 2 votes;
	/// - ...with an excess rank of 3 gets 3 votes;
	/// - ...with an excess rank of 4 gets 4 votes.
	pub struct Linear;
	impl Convert<Rank, Votes> for Linear {
	fn convert(r: Rank) -> Votes {
	(r + 1) as Votes
	}
	}
	/// Vote-weight scheme where all voters get one vote plus additional votes for every excess rank
	/// they have incrementing by one vote for each excess rank. I.e.:
	///
	/// - Each member with no excess rank gets 1 vote;
	/// - ...with an excess rank of 1 gets 2 votes;
	/// - ...with an excess rank of 2 gets 3 votes;
	/// - ...with an excess rank of 3 gets 6 votes;
	/// - ...with an excess rank of 4 gets 10 votes.
	pub struct Geometric;
	impl Convert<Rank, Votes> for Geometric {
	fn convert(r: Rank) -> Votes {
	let v = (r + 1) as Votes;
	v * (v + 1) / 2
	}
	}

Here is an example:
https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=eabd12199cf5bcad261dd1986e5c540c

Am I missing something or just a typo in the comments that this PR corrects? 🤞

[shawntabrizi]

bot merge