The Tour needs some polishing adjustments

[matheus23]

There appear two "Next" buttons with weird placement. I think that's confusing.
I also find it confusing that the other pages from the tour don't actually appear in the sidebar.

Also the headers for each step of the tour are:

• "A Tour of Iroh"
• "2. Endpoints"
• "2. Relays"
• "Discovery"
• "Protocols"
• "Routers"
• "Conclusion"

We should probably fix the numbering.

[matheus23]

Closed via #295