fix(docs): correct list_stores example in README

[rhamzeh]

Description

The List Stores example in the README was incorrectly referencing get_store instead of list_stores.

References

• Generated by: https://github.com/openfga/sdk-generator/pull/120
• Contributed by: @sebport0

Review Checklist

• [x] I have clicked on "allow edits by maintainers".
• [x] 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