Remove importing GlobalWeightDecayDefinition in split_table_batched_embeddings_ops (#2904)

Summary:
Pull Request resolved: #2904

f585120721 packaged `split_table_batched_embeddings_ops.py` but not `split_table_batched_embeddings_ops_training.py`. Thus it fails to import `GlobalWeightDecayDefinition` from an older version of `split_table_batched_embeddings_ops_training.py`.

Reviewed By: rumitdesai, spcyppt

Differential Revision: D60271207

fbshipit-source-id: 33499f7b125e3eaf0f1d3955786fea97c089c290

Author: Wang Zhou

fbgemm_gpu/fbgemm_gpu/split_table_batched_embeddings_ops.py

@@ -41,7 +41,6 @@
     CounterWeightDecayMode,
     DEFAULT_ASSOC,
     DenseTableBatchedEmbeddingBagsCodegen,
-    GlobalWeightDecayDefinition,
     GradSumDecay,
     INT8_EMB_ROW_DIM_OFFSET,
     LearningRateMode,