Fix DeiT-Tiny regression test for release/1.4.0 (#2595)

* Fix DeiT regression test

* update changelog

* temp

CHANGELOG.md

@@ -8,6 +8,7 @@ All notable changes to this project will be documented in this file.
 
 - Update ModelAPI configuration(<https://github.com/openvinotoolkit/training_extensions/pull/2564>)
 - Add Anomaly modelAPI changes (<https://github.com/openvinotoolkit/training_extensions/pull/2563>)
+- Fix IBLoss enablement with DeiT-Tiny when class incremental training (<https://github.com/openvinotoolkit/training_extensions/pull/2595>)
 
 ## \[v1.4.3\]
 

src/otx/algorithms/classification/adapters/mmcls/models/heads/custom_vision_transformer_head.py

@@ -31,3 +31,10 @@ def loss(self, cls_score, gt_label, feature=None):
             losses["accuracy"] = {f"top-{k}": a for k, a in zip(self.topk, acc)}
         losses["loss"] = loss
         return losses
+
+    def forward_train(self, x, gt_label, **kwargs):
+        """Forward_train fuction of CustomVisionTransformerClsHead class."""
+        x = self.pre_logits(x)
+        cls_score = self.layers.head(x)
+        losses = self.loss(cls_score, gt_label, feature=x)
+        return losses