[requirements] The version of zeroconf in upper constraints no longer supports python3.6

The zeroconf package seems to have dropped support for python3.6 since 0.38.0, see: https://github.com/jstasiak/python-zeroconf#0380. We currently have 0.38.1 in upper-constraints. My understanding was that the yoga release would still support python3.6. This is important for RHEL8 based distributions that only ship python3.6. Do we need to constrain zeroconf to a version <=0.37.0?