regexp/syntax: fix comment on p.literal and simplify
p.literal's doc comment said it returned a value but it doesn't.
While we're here, p.newLiteral is only called from p.literal,
so simplify the code by merging the two.
Change-Id: Ia357937a99f4e7473f0f1ec837113a39eaeb83d4
Reviewed-on: https://go-review.googlesource.com/c/go/+/222659
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>