feat: add --no-mirror option

[guedou]

Context

Cloning a repository with git clone --mirror may retrieve more git objects, and lead to more secrets being detected.

What has been done

By default ggshield now used --mirror. A new command line option could be used to disable this feature.

Validation

Clone https://github.com/nightwatchcybersecurity/gb_testrepo_delete?tab=readme-ov-filewith and without the new option.