cmd/guru: skip broken test for old Go versions for now
cmd/guru: skip broken test for old Go versions for now

Updates golang/go#24421

Change-Id: Iedcb629135802f78e8f149b377f34e49c8019fe9
Reviewed-on: https://go-review.googlesource.com/106435
Run-TryBot: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Reviewed-by: Andrew Bonventre <682ad9f487f614f19e8b7cc5d340bdc8e1c1b128@golang.org>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools