Should not convert HashAggregate if following shuffle is not converted

[EmilyMatt]

Describe the bug

Did not test this, so don't have a reproduction but should be easy to find a datatype that isn't supported and shuffle by that.
We don't currently have a mechanism to handle this

Steps to reproduce

No response

Expected behavior

No response

Additional context

No response

[andygrove]

This situation can be simulated easliy in a test by tagging the shuffle with a fallback reason before passing the plan to Comet