repos: remove unused Repo.UsePkgGoDev

UsePkgGoDev was added in CL 234677 to aid with a gradual migration
on golang.org. That redirection has been completed as of CL 275195,
and UsePkgGoDev is no longer meaningful nor used. Remove it, since
it's allowed per x/build's compatibilty policy, to keep things tidy.

Updates golang/go#36106.
Updates golang/go#39150.

Change-Id: If3f9bed7f215a7c572a2d7a9f25b3184a1e5362a
Reviewed-on: https://go-review.googlesource.com/c/build/+/289700
Trust: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Alexander Rakoczy <alex@golang.org>
diff --git a/repos/repos.go b/repos/repos.go
index d96a976..e2ba059 100644
--- a/repos/repos.go
+++ b/repos/repos.go
@@ -39,10 +39,6 @@
 	// https://golang.org/pkg/#subrepo.
 	// It should be plain text. Hostnames may be auto-linkified.
 	WebsiteDesc string
-
-	// usePkgGoDev controls whether the repo has opted-in to use
-	// pkg.go.dev for displaying documentation for Go packages.
-	usePkgGoDev bool
 }
 
 // ByGerritProject maps from a Gerrit project name ("go", "net", etc)
@@ -77,7 +73,7 @@
 	x("net", desc("additional networking packages"))
 	x("oauth2")
 	x("perf", desc("packages and tools for performance measurement, storage, and analysis"))
-	x("pkgsite", desc("home of the pkg.go.dev website"), usePkgGoDev(), noBuildAndNoDash)
+	x("pkgsite", desc("home of the pkg.go.dev website"), noBuildAndNoDash)
 	x("playground", noDash)
 	x("review", desc("a tool for working with Gerrit code reviews"))
 	x("scratch", noDash)
@@ -129,7 +125,6 @@
 func importPath(v string) modifyRepo { return func(r *Repo) { r.ImportPath = v } }
 
 func desc(v string) modifyRepo { return func(r *Repo) { r.WebsiteDesc = v } }
-func usePkgGoDev() modifyRepo  { return func(r *Repo) { r.usePkgGoDev = true } }
 
 // addMirrored adds a repo that's on Gerrit and mirrored to GitHub.
 func addMirrored(proj string, opts ...modifyRepo) {
@@ -202,7 +197,3 @@
 // at or is mirrored to. It returns the empty string if this repo has no
 // GitHub presence.
 func (r *Repo) GitHubRepo() string { return r.gitHubRepo }
-
-// UsePkgGoDev reports whether the repo has opted-in to use
-// pkg.go.dev for displaying documentation for Go packages.
-func (r *Repo) UsePkgGoDev() bool { return r.usePkgGoDev }