Fix: aten::matmul converter behavior with 1d tensors

[mfeliz-cruise]

Description

Previously the aten::matmul converter always left padded tensors to match dims between self and other. This behavior does not match PyTorch which right pads 1D tensors by 1 for other > self and left pads by 1 for self > other, removing the padded dim after the matmul in both cases.

Fixes # (issue)

Type of change

Please delete options that are not relevant and/or add your own.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project (You can use the linters)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas and hacks
• I have made corresponding changes to the documentation
• I have added tests to verify my fix or my feature
• New and existing unit tests pass locally with my changes
• I have added the relevant labels to my PR in so that relevant reviewers are notified

[peri044]

LGTM