The formatting verb '%#x' was used for uint32 values in CL 132956.
This fixes TestFormats.

Change-Id: I3ab6519bde2cb74410fdca14829689cb46bf7022
Reviewed-on: https://go-review.googlesource.com/133595
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>