BUG: wrong dateutil dependency link in dependency graph
- [x] I have checked that this issue has not already been reported.


Probably not a bug in pandas per se, but it might be useful to be aware of this: 
I noticed that the `python-dateutil` dependency on this github dependency graph page https://github.com/pandas-dev/pandas/network/dependencies points to https://github.com/clones/python-dateutil which is a strange 1-commit mirror repo from 2008, instead of the official repo https://github.com/dateutil/dateutil/
