chore: add back return value from is_seurat_convertible

[joyceyan]

Reason for Change

makes the change to remove is_seurat_convertible more backwards compatible friendly by continuing to return False. we can remove this return value entirely with a future release, though i think it should technically be part of a major update if we do

Changes

• returns False as the final tuple value always

Testing

updated unit tests

Notes for Reviewer

[ejmolinelli]

lgtm

I don't see anything missing.