Auto merge of #46954 - davidalber:fix-contributor-covenant-link, r=alexcrichton

Updating Contributor Covenant links

The current link 301s to a new destination.

```sh
$ curl -I http://contributor-covenant.org/version/1/3/0/
HTTP/1.1 301 Moved Permanently
Cache-Control: public, max-age=0, must-revalidate
Content-Length: 0
Content-Type: text/plain
Date: Fri, 22 Dec 2017 21:13:09 GMT
Location: https://www.contributor-covenant.org/version/1/3/0/
Age: 1
Connection: keep-alive
Server: Netlify
```

rust-lang/prev.rust-lang.org#994 fixes this in the Rust site.

Author: bors

CODE_OF_CONDUCT.md

@@ -35,6 +35,6 @@ And if someone takes issue with something you said or did, resist the urge to be
 
 The enforcement policies listed above apply to all official Rust venues; including official IRC channels (#rust, #rust-internals, #rust-tools, #rust-libs, #rustc, #rust-beginners, #rust-docs, #rust-community, #rust-lang, and #cargo); GitHub repositories under rust-lang, rust-lang-nursery, and rust-lang-deprecated; and all forums under rust-lang.org (users.rust-lang.org, internals.rust-lang.org). For other projects adopting the Rust Code of Conduct, please contact the maintainers of those projects for enforcement. If you wish to use this code of conduct for your own project, consider explicitly mentioning your moderation policy or making a copy with your own moderation policy so as to avoid confusion.
 
-*Adapted from the [Node.js Policy on Trolling](http://blog.izs.me/post/30036893703/policy-on-trolling) as well as the [Contributor Covenant v1.3.0](http://contributor-covenant.org/version/1/3/0/).*
+*Adapted from the [Node.js Policy on Trolling](http://blog.izs.me/post/30036893703/policy-on-trolling) as well as the [Contributor Covenant v1.3.0](https://www.contributor-covenant.org/version/1/3/0/).*
 
 [mod_team]: https://www.rust-lang.org/team.html#Moderation-team