CL 106463 introduced what seems to trim the "go:" prefix in pramas
comments twice, so "//go:go:foo" would be handled, too.
So either the strings.TrimPrefix or the [3:]-slicing is not needed.

I opted to remove the [3:]-slicing.

Change-Id: I1325bbc08a9be9ae100c5a7775b0a23f9ed0a419
Reviewed-on: https://go-review.googlesource.com/107256Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>