cmd/tip: make tip.golang.org also serve & redirect beta.golang.org to tip

We're turning down the old (and neglected) beta.golang.org godoc VM.
It's not different enough from tip.golang.org, which is more reliable
than it used to be.

Now beta.golang.org will just redirect to tip.

Updates golang/go#25978
Fixes golang/go#21073

Change-Id: Iae7fe4c82c14cec7381e75a2e214210d38b6e623
Reviewed-on: https://go-review.googlesource.com/c/120056
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
5 files changed
tree: aaff86badd6da68a5a28256909dd6ba69a2ee601
  1. cmd/