chore(archive/100-theorems-list): 83_friendship_graphs (#5727)
Cleaned up some lint and put it in terms of the new `simple_graph.common_neighbors`.
Co-authored-by: agusakov <39916842+agusakov@users.noreply.github.com>
Co-authored-by: Kyle Miller <kmill31415@gmail.com>
Co-authored-by: Bryan Gin-ge Chen <bryangingechen@gmail.com>
