Mastodon::Version instead of real version number in /api/v1/instance

[agateblue]

#2181 included version data in the payload returned from /api/v1/instance. However, it seems there is an issue, because here is what I get if I query https://mastodon.social/api/v1/instance:

{
	"uri": "mastodon.social",
	"title": "Mastodon",
	"description": "",
	"email": "eugen@zeonfederated.com",
	"version": "Mastodon::Version"
}

As you can see, instead of 1.3.0, which is displayed on the About page, we get the cryptic Mastodon::Version. Maybe I'm missing something, but I don't think this is intended behaviour.

This also affect other instances, such as https://mastodon.cloud/api/v1/instance.