fix: Use HTTPS instead of GIT protocol for cloning

[EBoisseauSierra]

Overview

Since 2022-01-11, GitHub has deprecated the usage of the git:// protocol in favour of the more secure https:// — cf. https://github.blog/2021-09-01-improving-git-protocol-security-github/#no-more-unauthenticated-git

This causes the following error when, e.g., cloning this repo as submodule:

The unauthenticated git protocol on port 9418 is no longer supported. Please see https://github.blog/2021-09-01-improving-git-protocol-security-github/ for more information.

As suggested in https://stackoverflow.com/a/70663683/5433628 we have then replaced URLs using git:// by their https:// equivalent.

Related issues

n/a