This label was added automatically by grind to remove gotos. As of
today, it's completely useless, as none of its uses need a label to
begin with.

While at it, remove all the redundant breaks too. Leave those that are
the single statement in a case clause body, as that's the style used
throughout std and cmd to clarify when cases are empty.

Change-Id: I3e20068b66b759614e903beab1cc9b2709b31063
Reviewed-on: https://go-review.googlesource.com/62950
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>