fix(ci): Use pinned dependencies for better security

[Siddhant-K-code]

Description

This pull request fixes the CI pipeline by using pinned dependencies for better security. It also updates the Docker Buildx setup.

References

Review Checklist

• [x] I have clicked on "allow edits by maintainers".
• [ ] I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• [x] The correct base branch is being used, if not main
• [ ] I have added tests to validate that the change in functionality is working as expected