Update _bio.html.haml (#8449)

On my local instance (https://ruby.social) we have a custom emoji for octocat (:octocat:). I would love to be able to use the emoji in the metadata for my profile. Instead of:

| github | https://github.com/phaedryx

It could be:

| :octocat: | https://github.com/phaedryx

(using a single emoji makes it easier to read the urls)