Bad link on news/changelog.html

[mattcaswell]

This page

https://www.openssl.org/news/changelog.html

contains this text

"This is the changelog for the master branch, the one that is currently
in active development. The plain-text / markdown version of this
document is available here:"

and a link to:

https://www.openssl.org/news/changelog.md

However, the 'changelog.md' page returns a "Page Not Found."

[levitte]

See #323