ITab is handled by decomposition.
The rule is vestigial. Remove it.

Change-Id: I6fdf3d14d466761c7665c7ea14f34ca0e1e3e646
Reviewed-on: https://go-review.googlesource.com/24718
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>