remove most 3.10 bw compat
Related to #3799117.
The boxes and entityvcomponent objects cannot really be removed as they
are still used throughout the code base (and possible cubes).
This may be caused by a non-working deprecation and needs some more
work.
../../doc/book usr/share/doc/cubicweb-documentation
../../doc/html usr/share/doc/cubicweb-documentation
../../debian/cubicweb-doc usr/share/doc-base/cubicweb-doc