Binary package page overuses <h2>

[Matthew Paul Thomas]

A binary package page, such as <https://launchpad.net/ubuntu/hardy/i386/python-xml/0.8.4-10build2>, has an <h2> heading for "Package relationships". It then has <h2> headings for "Depends on", "Conflicts [with]", "Provides", etc. But these are particular kinds of package relationships, so their headings should be <h3> instead.