The returned email by the GitHub API is the user's publicly visible
email address (or null if the user has not specified a public email
address in their profile)
The reason is that Gitea plan to be GitHub-compatible so it makes sense
to just modify GitHubImport a bit for now, and hopefully we can change
it to GitHubishImport once Gitea is 100%-compatible.
Signed-off-by: Rémy Coutable <remy@rymai.me>