Switch baseURL to www.apertis.org

Now that the site is live, switch the baseURL from
"https://docs.pages.apertis.org/apertis-website/" to
"https://www.apertis.org/

" so that users aren't pushed onto the
docs.pages.a.o site when traversing the site.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>