Deprecated CycleGraph usage needs removing.

[josephcbradley]

Rogue instance of CycleGraph in test/louvain.jl:

 Warning: `CycleGraph(n)` is deprecated, use `cycle_graph(n)` instead.
│   caller = macro expansion at louvain.jl:72 [inlined]
└ @ Core ~/work/Graphs.jl/Graphs.jl/test/community/louvain.jl:72

Happy to take.

[Krastanov]

Thanks! Please submit a PR if you have a chance.