Minor improvement on the decomposition of upsample_bilinear (#101682)

This is how it's done in core.
Pull Request resolved: #101682
Approved by: https://github.com/ngimel

torch/_decomp/decompositions.py

@@ -2780,19 +2780,15 @@ def upsample_bilinear2d(
         if align_corners:
             h_scale_factor = (in_h - 1) / (out_h - 1)
         else:
-            h_scale_factor = (
-                in_h / (in_h * scales_h) if scales_h is not None else in_h / out_h
-            )
+            h_scale_factor = 1.0 / scales_h if scales_h is not None else in_h / out_h
     else:
         h_scale_factor = 0.0
 
     if out_w > 1:
         if align_corners:
             w_scale_factor = (in_w - 1) / (out_w - 1)
         else:
-            w_scale_factor = (
-                in_w / (in_w * scales_w) if scales_w is not None else in_w / out_w
-            )
+            w_scale_factor = 1.0 / scales_w if scales_w is not None else in_w / out_w
     else:
         w_scale_factor = 0.0