[FSSDK-12368] Remove unused imports from test file

Remove unused imports flagged by ruff:
- unittest (using unittest.mock instead)
- decision_service (not used)
- OptimizelyDecideOption (not used)
- enums (not used)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: Mat001

tests/test_local_holdouts.py

@@ -18,16 +18,12 @@
 """
 
 import json
-import unittest
 from unittest import mock
 
-from optimizely import decision_service
 from optimizely import error_handler
 from optimizely import logger
 from optimizely import optimizely as optimizely_module
-from optimizely.decision.optimizely_decide_option import OptimizelyDecideOption
 from optimizely import entities
-from optimizely.helpers import enums
 from tests import base