fix: Ensure executor is shutdown

[jimmyjames]

Description

Calls shutdown on the executor in batchCheck

References

Fixes #132

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

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 31.72%. Comparing base (5c39f01) to head (972cc80).

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #133      +/-   ##
============================================
+ Coverage     31.71%   31.72%   +0.01%     
  Complexity      885      885              
============================================
  Files           169      169              
  Lines          6310     6311       +1     
  Branches        699      699              
============================================
+ Hits           2001     2002       +1     
  Misses         4207     4207              
  Partials        102      102              

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[rhamzeh]

@jimmyjames can we make sure we're doing the same in non-transactional writes?

[jimmyjames]

@jimmyjames can we make sure we're doing the same in non-transactional writes?

Yep; there's no other usage of executor in the SDK.