[hooks/syncschema] avoid altering a dropped table If the constraint's rdef is being removed, CWConstraintDelOp doesn't need to do anything. Otherwise it may try to alter a removed table/column. Closes #4154549

if versions_map['cubicweb'][0] == (3, 7, 4):
    config['http-session-time'] *= 60
    config['cleanup-session-time'] *= 60
    config['cleanup-anonymous-session-time'] *= 60