[test] Replace symlinks in legacy_cubes by real copies
This solves a "python setup.py build" issue on my machine.
Copying these files should not be a big deal because they
have been dropped in the "default" branch and we would not
touch them in 3.26 branch.
Document: cubicweb-doc
Title: CubicWeb Documentation
Author: Logilab
Abstract: Some base documentation for CubicWeb users and developers
Section: Programming
Format: HTML
Index: /usr/share/doc/python-cubicweb-documentation/html/index.html
Files: /usr/share/doc/python-cubicweb-documentation/html/*