Change the gpt crate repo URL to the redox gitlab.
Instead of depending on https://github.com/4lDO2/gpt.git, partitionlib now depends on https://gitlab.redox-os.org/redox-os/gpt.git.
Instead of depending on https://github.com/4lDO2/gpt.git, partitionlib now depends on https://gitlab.redox-os.org/redox-os/gpt.git.