Wrong package version shown in index page

Reported by @bartm in package versions at mentors

Index page for packages should report the last uploaded version for a package.

Template for packages already asks for the last item:

https://salsa.debian.org/mentors.debian.net-team/debexpo/blob/live/debexpo/templates/packages/list.mako#L23

<td class="lines">${ package.package_versions[-1].version }</td>

However, query from the DB is not sorted:

https://salsa.debian.org/mentors.debian.net-team/debexpo/blob/live/debexpo/controllers/packages.py#L94