Fix content failing to load when served from HTTPS due to insecure content.

[Joncom]

In his 2014 update to this article, @paulirish says:

If the asset you need is available on SSL, then always use the https:// asset.

Allowing the snippet to request over HTTP opens the door for attacks like the recent Github Man-on-the-side attack. It’s always safe to request HTTPS assets even if your site is on HTTP, however the reverse is not true.

[Joncom]

In other words, this will allow your script to be used by applications served over HTTPS, which is currently broken. There's no downside here.