Remove unused imports from cluster_wrapper_test

Author: arovir01

tensorflow_model_optimization/python/core/clustering/keras/cluster_wrapper_test.py

@@ -24,16 +24,13 @@
 from tensorflow_model_optimization.python.core.clustering.keras import cluster_config
 from tensorflow_model_optimization.python.core.clustering.keras import cluster_wrapper
 from tensorflow_model_optimization.python.core.clustering.keras import clusterable_layer
-from tensorflow_model_optimization.python.core.clustering.keras import clustering_registry
 
 keras = tf.keras
 errors_impl = tf.errors
 layers = keras.layers
 test = tf.test
 
 CentroidInitialization = cluster_config.CentroidInitialization
-ClusterRegistry = clustering_registry.ClusteringRegistry
-ClusteringLookupRegistry = clustering_registry.ClusteringLookupRegistry
 
 
 class NonClusterableLayer(layers.Dense):