[test] use assertIn where appropriate
Automatically generated with:
find -name unittest_*.py -o -name test_*.py | xargs sed -i -e 's/assertTrue(\([^,]*\) in \([^,]*\))/assertIn(\1, \2)/'
usr/lib/PY_VERSION/*-packages/cubicweb/entities/
usr/lib/PY_VERSION/*-packages/cubicweb/ext/
usr/share/cubicweb/cubes/
usr/lib/PY_VERSION/*-packages/cubicweb/*.py