Renamed Graphs to Stats

**What does this MR do?**
It renames the menu item Graphs to Status, I hope this prevents some unclearness about what Network and Graphs means. Since I almost always click on Graphs when I want to see the Network Graphs.

**Relevant issues**
It was suggested by @zyphrax in https://github.com/gitlabhq/gitlabhq/issues/7505