Add is_weighted() call to FPEBC (#3140)

Summary:
Pull Request resolved: #3140

Resolving Bug surfaced here: https://docs.google.com/document/d/1K5V1UGRj9Hn85dV6Ka8Fa1nLr7TwsQGGdn6cmFqS75s/edit?tab=t.0

Reviewed By: aliafzal

Differential Revision: D77331144

fbshipit-source-id: 8d5570bdb8a6f8c66acc9857a2165de07900b3d3

Author: aporialiao

torchrec/modules/fp_embedding_modules.py

@@ -146,6 +146,9 @@ def split(
             assert isinstance(self._feature_processors, FeatureProcessorsCollection)
             return self._feature_processors, self._embedding_bag_collection
 
+    def is_weighted(self) -> bool:
+        return self._embedding_bag_collection.is_weighted()
+
     def forward(
         self,
         features: KeyedJaggedTensor,