af_unix: remove redundant lockdep class

af_unix: remove redundant lockdep class

After commit 581319c58600 ("net/socket: use per af lockdep classes for sk queues")
sock queue locks now have per-af lockdep classes, including unix socket.
It is no longer necessary to workaround it.

I noticed this while looking at a syzbot deadlock report, this patch
itself doesn't fix it (this is why I don't add Reported-by).

Fixes: 581319c58600 ("net/socket: use per af lockdep classes for sk queues")
Cc: Paolo Abeni <[email protected]>
Signed-off-by: Cong Wang <[email protected]>
Acked-by: Paolo Abeni <[email protected]>
Signed-off-by: David S. Miller <[email protected]>