Update gitleaks generation script

[Aleridia]

Gitleaks changes its rule format, so we need to update the script

[mazen160]

Hi @Aleridia ,

Thank you very much for your PR. I have updated it separately as there was a merge conflict.

The change is pushed on this commit:
18fc19d

The only difference is that the --low-confidence rules should be unreliable and super noisy. That's why we may want to avoid converting them for the time being, but it's good to document for future improvements.