fix(docs): fix readme (#34)

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<!-- Provide a brief summary of the changes -->
Update README

## Description
<!-- Provide a detailed description of the changes -->

Update the SpEL in the README according to
[examples](https://docs.spring.io/spring-security/reference/servlet/authorization/method-security.html#using-authorization-expression-fields-and-methods)

## References
<!-- Provide a list of any applicable references here (GitHub Issue,
[OpenFGA RFC](https://github.com/openfga/rfcs), other PRs, etc..) -->

## Review Checklist
- [x] I have clicked on ["allow edits by
maintainers"](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/allowing-changes-to-a-pull-request-branch-created-from-a-fork).
- [ ] I have added documentation for new/changed functionality in this
PR or in a PR to [openfga.dev](https://github.com/openfga/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

README.md

@@ -118,7 +118,7 @@ security to protect access to resources using FGA:
 
 ```java
 // Method body will only execute if the FGA check returns true. 403 otherwise.
-@PreAuthorize("@fga.check('document', #docId, 'reader', 'user', 'authentication?.name')")
+@PreAuthorize("@fga.check('document', #docId, 'reader', 'user', authentication?.name)")
 public Document getDocument(@PathVariable String docId) {
     return repository.findById(id);
 }