Doc: Fix incorrect folder name & pre-commit setup in CONTRIBUTING.md

[SSK-14]

Description

This PR contains a very small documentation change in the CONTRIBUTING.md file. The folder name in the command after cloning the repository was incorrect and facing error with pre-commit setup, and I have fixed it to reflect the correct name and command.

Related Issue(s)

While running this:

python -m pre-commit install

/Users/.../OSS/NeMo-Guardrails/venv/bin/python: No module named pre-commit

Checklist

• [X] I've read the CONTRIBUTING guidelines.
• [X] I've updated the documentation if applicable.
• [X] I've added tests if applicable.
• [x] @mentions of the person or team responsible for reviewing proposed changes.

[Pouyanpi]

Thank you @SSK-14 for your PR!