[pkg] Remove explicit Depends on Python packages for python3-cubicweb As suggested by Denis Laxalde, we can let pybuild generate the list of Depends from the egg requirements. The list we get is slightly less specific in terms of needed versions, but given the age of the previous ones, it's unlikely to cause issues. Also we lose python3-six from the list… which is correct as it was removed from the dependencies in 26744ad37953.

### Requirements for tests in various cubicweb/**/test directories. ###

## shared by several test folders
docutils
webtest

## cubicweb/test
Pygments
pycryptodome
#fyzz XXX pip install fails

## cubicweb/devtools/test
flake8

## cubicweb/hooks/test
psycopg2-binary

## cubicweb/pyramid/test
pyramid >= 1.5.0
waitress >= 0.8.9
wsgicors >= 0.3
pyramid_multiauth
repoze.lru

## cubicweb/sobject/test