fix qunit tests in devtools
https://jenkins.logilab.org/job/cubicweb-default/465/TOXENV=py3-misc,distributions=cubicweb/testReport/cubicweb.devtools.test.unittest_qunit/QUnitTestCaseTC/test_simple_failure/ says that xauth is missing.
Add it to the dev requirements.
c.f. https://forge.extranet.logilab.fr/cubicweb/cubicweb/-/jobs/25782
original ticket : https://www.cubicweb.org/ticket/17262151