benchstat: add godoc links from legacy benchstat to the new one

Change-Id: Ice0f8599b2560fe5dd2d8a291381424cef2c241d
Reviewed-on: https://go-review.googlesource.com/c/perf/+/837985
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

benchstat/doc.go

diff --git a/benchstat/doc.go b/benchstat/doc.go
index 0ca6010..d14cb7c 100644
--- a/benchstat/doc.go
+++ b/benchstat/doc.go
@@ -8,6 +8,6 @@
 // version of the benchstat command.
 //
 // Deprecated: The latest version of benchstat can be found at
-// golang.org/x/perf/cmd/benchstat. To work with benchmark data, see
-// golang.org/x/perf/benchproc and golang.org/x/perf/benchmath.
+// [golang.org/x/perf/cmd/benchstat]. To work with benchmark data, see
+// [golang.org/x/perf/benchproc] and [golang.org/x/perf/benchmath].
 package benchstat