Currently, when we access the URL https://www.grpc.io, it is redirected to https://www.grpc.io automatically.
So this commit aims to replace **HTTP** to **HTTPs** for security.
Since we implemented docs versioning, the default url is
https://cockroachlabs.com/docs/stable instead of
https://cockroachlabs.com/docs. We have a redirect in place
from /docs to /docs/stable, so existing links aren't broken,
but it's a better user experience to bypass the redirect.