Documentation search bar is not relative to the version of Jetty

If you browse the Jetty 10 documentation, and search for anything in the search bar, all the results are for Jetty 12 not Jetty 10.

We should only search the documentation for the version of Jetty that you are viewing. Or at least prioritize the current version in the results.

Start by locating the documentation search bar and comparing searches from the Jetty 10 and Jetty 12 documentation sites. Trace how the selected documentation version is passed to the search, then verify that Jetty 10 searches return Jetty 10 results or prioritize them appropriately.

Written by the indexing model from the issue text.