Fix typo in docs/index.md

[logan2d5]

Summary

Change http to https in the document.

Checklist

• [ x] I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• [ x] I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• [ x] I've updated the documentation accordingly.

[Kludex]

Thanks :)