tox.ini: Work around build failure due to upstream release

This fixes the master build [1]

[1] https://jenkins.softwareheritage.org/job/DLS/job/tests/1210/console

tox.ini

@@ -7,6 +7,7 @@ extras =
 deps =
   swh.core[http] >= 0.0.61
   swh.scheduler[testing] >= 0.5.0
+  amqp != 5.0.4
   pytest-cov
   dev: ipdb
 commands =