Remove deprecated From<Vertex> for usize implementation

src/models/append_graph.rs

@@ -4,12 +4,6 @@ use crate::traits::GraphTopology;
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 pub struct Vertex(usize);
 
-impl From<Vertex> for usize {
-    fn from(v: Vertex) -> usize {
-        v.0
-    }
-}
-
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 pub struct Incidence(usize);