Updates floor division to use floor division operator

Summary:
Performing floor division with torch.div is deprecated and will soon throw a runtime error. This diff updates the floor division to use the floor division operator.

Created from Diffusion's 'Open in Editor' feature.

Reviewed By: myleott

Differential Revision: D21848480

fbshipit-source-id: c9374e9406f4ba388f30315294eee7a2a4fcfecc

fairseq/search.py

@@ -335,7 +335,7 @@ def step(self, step: int, lprobs, scores):
             k,
         )
 
-        final_beams = torch.div(final_indices, k)
+        final_beams = final_indices // k
 
         for i in range(bsz):
             final_indices[i] = indices[i][final_indices[i]]