fix: remove duplicate --use-latest pytest option in spin conftest

[odncode]

Summary

Remove duplicate --use-latest pytest option registration that prevents the unit test suite from collecting.

Problem

Running pytest test/unit/ fails during collection with:

ValueError: option names {'--use-latest'} already added

--use-latest is registered in both test/unit/conftest.py (added in #3040) and test/unit/spin/conftest.py (from #2506). pytest raises on the duplicate.

Fix

Remove pytest_addoption from test/unit/spin/conftest.py. The root test/unit/conftest.py already registers the option and it applies to all subdirectories.

Testing

State	Result
Before	pytest test/unit/ fails with collection error
After	468 passed, 1 failed, 19 skipped, 21 errors

Note: The 1 failure (complex_dag) and 21 errors (secrets/system_context tests) are pre-existing infrastructure issues unrelated to this change.

[greptile-apps]

Greptile Summary

This PR removes a duplicate pytest_addoption registration for --use-latest in test/unit/spin/conftest.py. The option was already registered in the parent test/unit/conftest.py (added in #3040), causing pytest to raise a ValueError during collection when running the full unit suite.

• Deletes the redundant pytest_addoption function from test/unit/spin/conftest.py; the root-level registration already covers all subdirectories.
• The spin conftest still consumes the option correctly via request.config.getoption("--use-latest", default=False), so no functional behavior changes.

Confidence Score: 5/5

The change is minimal and correct — removing a duplicate option registration that broke pytest collection with no effect on runtime test behavior.

The deleted code is a duplicate of an already-present registration in the parent conftest. The --use-latest option continues to be registered once and consumed correctly in the spin fixtures. No logic or behavior changes; the only effect is fixing the collection crash.

No files require special attention.

Important Files Changed

Filename	Overview
test/unit/spin/conftest.py	Removes duplicate pytest_addoption registration for --use-latest; the option is already registered in the parent test/unit/conftest.py and continues to be consumed correctly via request.config.getoption.

_{Reviews (2): Last reviewed commit: "style: fix black formatting in spin conf..." | Re-trigger Greptile}

[talsperre]

Looks good to me. We can merge once the tests pass.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (master@4871fb1). Learn more about missing BASE report.

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #3205   +/-   ##
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  Coverage          ?   28.31%           
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  Files             ?      381           
  Lines             ?    52353           
  Branches          ?     9242           
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  Hits              ?    14826           
  Misses            ?    36587           
  Partials          ?      940           

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