record_listed_origins raises "CardinalityViolation: ON CONFLICT DO UPDATE command cannot affect row a second time"

CardinalityViolation: ON CONFLICT DO UPDATE command cannot affect row a second time
HINT:  Ensure that no rows proposed for insertion within the same command have duplicate constrained values.

  File "flask/app.py", line 1813, in full_dispatch_request
    rv = self.dispatch_request()
  File "flask/app.py", line 1799, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "swh/core/api/negotiation.py", line 153, in newf
    return f.negotiator(*args, **kwargs)
  File "swh/core/api/negotiation.py", line 81, in __call__
    result = self.func(*args, **kwargs)
  File "swh/core/api/__init__.py", line 460, in _f
    return obj_meth(**kw)
  File "swh/core/db/common.py", line 62, in _meth
    return meth(self, *args, db=db, cur=cur, **kwargs)
  File "swh/scheduler/backend.py", line 253, in record_listed_origins
    fetch=True,
  File "psycopg2/extras.py", line 1281, in execute_values
    cur.execute(b''.join(parts))
  File "psycopg2/extras.py", line 243, in execute
    return super(RealDictCursor, self).execute(query, vars)

Sentry link: SWH-SCHEDULER-4S

This is triggered by the Github lister: SWH-LISTER-2Y

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Migrated from T3344 (view on Phabricator)