feat: Switch AddMM decomp to Torch version

[gs-olive]

Description

• Remove custom decomposition for addmm, since Torch now provides one
• Leave test cases present as a sanity check

Type of change

• Minor implementation switch

Checklist:

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

[github-actions]

Code conforms to Python style guidelines

[github-actions]

Code conforms to C++ style guidelines

[github-actions]

Code conforms to C++ style guidelines

[github-actions]

Code conforms to Python style guidelines

[gs-olive]

Will be addressed by PR for #2398