Documentation Mistake: `SccGraph::new(n)` should refer to vertices, not edges

[Ryoga-exe]

The function SccGraph::new(n: usize) is intended to create a directed graph with $n$ vertices and $0$ edges.
However, the current documentation mistakenly refers to n as the number of edges, which is incorrect.

Current documentation:

ac-library-rs/src/scc.rs

Line 39 in 89568c5

/// Creates a new `SccGraph` with `n` edges.

This should be corrected to refer to vertices, not edges.