Docs: Clarify where to see the traffic analytics (#12821)
In https://docs.readthedocs.com/platform/stable/traffic-analytics.html,
the user is instructed to go to the "Admin panel" and then click on
"Traffic analytics" to check a project's traffic data.
But the "Admin panel" that it is referring to is actually the "Settings"
panel. So I changed it so that its easier for someone reading it to
actually find the "Traffic analytics" section.