Removing a vertex doesn't delete the incoming edges of associated vertices

[rkrump]

Describe the bug It looks like #51 is not fully fixed yet. The _inEdgeMap of the target vertices still contain the invalid edges.

To Reproduce Steps to reproduce the behavior:

1. Create directed graph with the vertices "Hello" & "Hi"
2. Add an edge from "Hello" to "Hi"
3. Delete the vertex "Hello"
4. incomingEdgesOf on "Hi" still reports the edge from the source vertex "Hello"

import { DirectedGraph } from "graph-typed";

let graph = new DirectedGraph();

graph.addVertex("Hello");
graph.addVertex("Hi");

graph.addEdge("Hello", "Hi");

graph.deleteVertex("Hello");

console.log(graph.incomingEdgesOf("Hi"));

Expected behavior Deleting a vertex results in all associated edges being deleted from all sides.

[zrwusa]

Because of our oversight, we did not remove edges with incoming adjacency nodes when deleting a node. This bug has been fixed in version 1.49.4.