Fix the header in the generated zptrace*_linux.go files to consistently
use single space after a period.

Change-Id: I527f27a68e14bc103639b1dd5734ec06ae267e01
Reviewed-on: https://go-review.googlesource.com/73875
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>