Update structures.ops.transforms.bbox3droi

[ashutoshsingh0223]

Motivation

The method, structures.ops.transforms.bbox3droi returns rois as a tensor. There was a condition that led to returns of tensors with 7 or 8 size on dim 1 depending on the fulfillment of the condition. The change fixes the shape to 8 without any other changes. This is necessary because the downstream modules that use this output expect a size of 8 on dim 1 not 7. See Single3DRoIPointExtractor.forward

Modification

The change fixes the shape of the return of structures.ops.transforms.bbox3droi to 8 on dim 1 without any other changes. This is necessary because the downstream modules that use this output expect a size of 8 on dim 1 not 7. See Single3DRoIPointExtractor.forward

BC-breaking (Optional)

No since all the downstream users of this method expect a size of 8 on dim 1 for rois, 1 for image index in batch and rest 7 for the bbox attributes.

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects.
4. The documentation has been modified accordingly, like docstring or example tutorials.