reflect: remove depth from deepequal recursion

We aren't using it for anything. The visited map will terminate
any recursion for us.

Change-Id: I36e6bd8e34952123c2ed46323067e42928ec7168
Reviewed-on: https://go-review.googlesource.com/c/go/+/238759


Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>