html: entity spec link broken

[pierrre]

On https://tip.golang.org/src/html/entity.go
there is a link to http://www.whatwg.org/specs/web-apps/current-work/multipage/named-character-references.html.
This link doesn't work anymore.

The new URL is probably https://html.spec.whatwg.org/multipage/named-characters.html (not sure)

[gopherbot]

Change https://golang.org/cl/52970 mentions this issue: html: updated entity spec link