reflect: remove dead v.typ assignment

v is not a pointer receiver, and v.typ isn't used in the lines below.
The assignment is dead. Remove it.

Keep the comment, as it refers to the whole case block and not just the
removed line.

Change-Id: Icb2d20c287d9a41bf620ebe5cdec764cd84178a7
Reviewed-on: https://go-review.googlesource.com/43134


Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>