image/color/palette: add godoc link to generator program
CL 535196 accidentally changed a generated file without changing
the generator program. This updates the generator program to generate
the current file.
Change-Id: I06513c9b29c7ca4084ac3768229ef8793efe0218
Reviewed-on: https://go-review.googlesource.com/c/go/+/625901
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com>
Commit-Queue: Ian Lance Taylor <iant@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>