Gravatar URLs are md5 instead of sha256

[theogravity]

Gravatar recommends sha256 instead of md5

It seems the rationale is that it's possible to reverse-engineer the e-mail address from the md5 hash.

Automattic/wp-calypso#87886

Description

I think FA is using md5 instead of sha256.

At some point, gravatar started recommending sha256, as their docs say to use it:

https://docs.gravatar.com/api/avatars/hash/

[mooreds]

Thanks for the enhancement suggestion, @theogravity ! We have a backlog of work, but when we review the admin UI, we'll see if we can get this work fitted in.