`dstack` doesn't work if the repo contains a submodule with SSH URL

[peterschmidt85]

Steps to reproduce:

1. Create a repo that has a submodule with an SSH URL.

Example of .gitmodules:

[submodule "test-1"]
        path = test-1
        url = git@github.com:peterschmidt85/test-1.git

2. Submit a run.

Actual behavior:

"git@github.com:peterschmidt85/test-1.git": first path segment in URL cannot contain colon

Root cause: go-git/go-git#488