Modify new queue cleanup protobuf fields from 'required' to 'optional'

As discussed in https://gitlab.cern.ch/cta/operations/-/issues/937#note_6275529, there is a problem in version 4.8.0-1 that is causing the parsing of old queue objects to fail.

This is probably the reason why there is an overload of the objectstore that is causing the frontend to fail: https://gitlab.cern.ch/cta/operations/-/issues/937.

This issue should be fixed by modifying the queue cleanup protobuf fields from 'required' to 'optional'.