Remove pooling layer for TokenClassificationModel (#351)

* add_pooling_layer

* Revert "add_pooling_layer"

This reverts commit 607c9cf.

* use BertModel::new_with_optional_pooler
- in BertForTokenClassification

---------

Co-authored-by: Mauro Sciancalepore <mauro.sciancalepore@treatwell.com>

src/bert/bert_model.rs

@@ -989,7 +989,7 @@ impl BertForTokenClassification {
     {
         let p = p.borrow();
 
-        let bert = BertModel::new(p / "bert", config);
+        let bert = BertModel::new_with_optional_pooler(p / "bert", config, false);
         let dropout = Dropout::new(config.hidden_dropout_prob);
         let num_labels = config
             .id2label