[x/blog] content: fix link in pkg.go.dev-2020.article
[x/blog] content: fix link in pkg.go.dev-2020.article

The link text for "file an issue on the Go issue tracker" was
https://golang.org/x/discovery-feedback (which is a 404).

It is fixed to be https://golang.org/s/discovery-feedback.

Fixes golang/go#36968

Change-Id: Ia46ac439544e047bd469c7814c85469d8a5395a2
Reviewed-on: https://go-review.googlesource.com/c/blog/+/217400
Reviewed-by: Andrew Bonventre <682ad9f487f614f19e8b7cc5d340bdc8e1c1b128@golang.org>
X-Blog-Commit: 09ac0697399413df587b2f19b74aabf16fa23c99

golang/website,golang/website,golang/website,golang/website,golang/website,golang/website,golang/website