use "git" protocol for submodule prevent access without a github account

[yuchangyuan]

see https://github.blog/2021-09-01-improving-git-protocol-security-github/

without a github account, git:// is not accessible. so I think we should convert all 'git://' of submodule URL to 'https://'.

[KlausKoder]

Just in case you didn't solve this issue. The simple fix is to add the following to your ~/.gitconfig:

[url "https://github.com/"]
	insteadOf = git@github.com: