[inductor] Fix args in sink_cat_after_pointwise (#94416)
Summary:
Silly me, I did not realize that dim could be a regular arg as well as
a kwarg in this pass.
Test Plan: New unit test.
Differential Revision: D43098594
Pull Request resolved: https://github.com/pytorch/pytorch/pull/94416
Approved by: https://github.com/jansel
