change hornet document addNeighbor's neighbors' port from 14265 to 15600

[EasonC13]

Description of change

page on https://docs.iota.org/docs/hornet/1.1/references/api-reference#addneighbors

I try these API and found out that the neighbor's port is not 14265 but 15600 . So I fix the document to prevent others like me spend lots of time to figure out this mistake.

Bug fix (a non-breaking change which fixes an issue)

Change Hornet Document's addNeighbor example's neighbors' port from 14265 to 15600