ci: pin action versions by sha

[ewanharris]

Description

We already do this in https://github.com/openfga/action-openfga-deploy but not here, we should pin by sha to improve the security of these actions as a tag is immutable and can be changed,

References

Review Checklist

• 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]
• 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

If you haven't done so yet, we would appreciate it if you could star the OpenFGA repository. :)