internal/goexperiment: update location of baseline experiment in comment

It moved in CL 310731.

Change-Id: I97340848b55e327d3b25949ec3850aec33448bbe
Reviewed-on: https://go-review.googlesource.com/c/go/+/644955
Reviewed-by: Carlos Amedee <carlos@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>

Author: ianlancetaylor

src/internal/goexperiment/flags.go

@@ -51,7 +51,7 @@ package goexperiment
 // tags, experiments use the strings.ToLower of their field name.
 //
 // For the baseline experimental configuration, see
-// objabi.experimentBaseline.
+// [internal/buildcfg.ParseGOEXPERIMENT].
 //
 // If you change this struct definition, run "go generate".
 type Flags struct {