Banners that switch the version of docs should not redirect to the home page

**Describe the problem/challenge you have**
When viewing ytt doc, I see a banner that says:
```
Documentation for version v0.38.0 is no longer actively maintained.
The version you are currently viewing is a static snapshot.
For up-to-date documentation, see the latest version.
```
but when I click on [`latest version`]() it changes to latest version, and brings me to the home page of the ytt docs.

**Describe the solution you'd like**
I would like the site to change the version but try and stay on the page I am looking at when the version changes.

The issue does not name a file or test. Start by locating the documentation version banner and its “latest version” link, then inspect how the link maps pages between versions. Done means switching versions preserves the page being viewed when an equivalent page exists, rather than always opening the documentation home page.

Written by the indexing model from the issue text.