Rockspec: use HTTPS instead of the Git protocol

[mhinz]

The Git protocol (port 9418) is blocked by many firewalls. Use the HTTPS
protocol (port 443) instead.

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Problem arised here: neovim/neovim#3769

[mpeterv]

Thanks! Though I think that it should be git+https://, not https://, or else luarocks would interpret the url as an address of an archive to download. I'll update the rockspec and comment here, but you'll have to change the neovim build config for luacheck to get the rockspec from the master branch.

[mhinz]

I think that it should be git+https://, not https://

Oops, you're right.

change the neovim build config for luacheck to get the rockspec from the master branch

Will do.

[mpeterv]

Done.