encoding/gob: update decgen to generate current dec_helpers
I edited dec_helpers.go without realizing that it is a generated file.
Fix the generator to generate the current version (which generates
a small comment change).
Change-Id: I70e3bc78eb0728d23c08972611218f288dc1d29c
Reviewed-on: https://go-review.googlesource.com/c/go/+/479117 Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Andrew Ekstedt <andrew.ekstedt@gmail.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Auto-Submit: Ian Lance Taylor <iant@golang.org> Reviewed-by: Rob Pike <r@golang.org> Reviewed-by: Heschi Kreinick <heschi@google.com>