message: Fix CreateDepthwiseBackpropFilter.
  Summary:
  Dimensions of the output tensor were being reshaped using the input
  tensor shape.
  Resolves T4475
  Reviewers: jamesn, davidn, georgep
  Maniphest Tasks: T4475
diff: @@ -371,7 +371,7 @@ StatusOr<poplar::program::Program> CreateDepthwiseBackpropFilter(
  // Move 'G' parts of the B back to I
  out = out.reshapePartial(1, 2, {n_g, out.dim(1) / n_g});
  out = out.dimShufflePartial({1}, {0});
  - out = out.reshapePartial(0, 2, {in.dim(0) * in.dim(1)});
  + out = out.reshapePartial(0, 2, {out.dim(0) * out.dim(1)});
  out = ShuffleConvolutionOutputToTensorflow(conv, out);
  