Fixup python-pyxattr-doc interaction with old python-pyxattr

Fixup python-pyxattr-doc interaction with old python-pyxattr

I thought that as the html files are in a new location, we don't need
replaces/breaks; but there's the doc base file, with the same name :(

Fix things up (fortunately re-reading the policy shows that just
installing the new -doc package won't remove the old python-pyxattr,
but upgrade it to newer one), and also add the -doc package to
suggests on the -pyxattr ones.