Remove unused imports from scheduler_test_utils.py (#2654)

Summary:
Pull Request resolved: #2654

These unused imports are causing Flake8 errors

Reviewed By: esantorella

Differential Revision: D61214103

fbshipit-source-id: 67024146b27fd235255def3cc031381fc5d33cf5

ax/service/tests/scheduler_test_utils.py

@@ -37,14 +37,8 @@
 from ax.metrics.branin_map import BraninTimestampMapMetric
 from ax.modelbridge.cross_validation import compute_model_fit_metrics_from_modelbridge
 from ax.modelbridge.dispatch_utils import choose_generation_strategy
-from ax.modelbridge.generation_strategy import (
-    GenerationNode,
-    GenerationStep,
-    GenerationStrategy,
-)
-from ax.modelbridge.model_spec import ModelSpec
+from ax.modelbridge.generation_strategy import GenerationStep, GenerationStrategy
 from ax.modelbridge.registry import Models, ST_MTGP_trans
-from ax.modelbridge.transition_criterion import MaxTrials, MinTrials
 from ax.runners.single_running_trial_mixin import SingleRunningTrialMixin
 from ax.runners.synthetic import SyntheticRunner
 from ax.service.scheduler import (