fix latest_time for exploded edge on PersistentGraph for edges that are deleted at the same time as created

[ljeub-pometry]

What changes were proposed in this pull request?

fixes:

G1 = PersistentGraph()

G1.add_edge(1, 1, 2, properties={"message":"hi"})
G1.delete_edge(1, 1, 2)

print(f"G1's edges are {G1.edges.explode()}")

which was returning

G1's edges are Edges(Edge(source=1, target=2, earliest_time=1, latest_time=9223372036854775807, properties={message: hi}))

but the latest_time should have been 1.

How was this patch tested?

Added test for this case

[narnolddd]

Yay! Looks good :)