Suppress up/down arrow for search results columns that cannot be sorted

Overview: If a search results column is not sortable, the up/down arrows should be suppressed (not sure if this should be a bug or story, so wrote it up as a bug)

Steps to Reproduce:

1. Log into FOLIO-testing as diku_admin
2. Go to Orders app and view the PO line search results
3. Click on the Product ID and the Fund code column headers

Expected Results: These are not sortable fields. They do not sort (correct) and I should not see the up/down arrow (incorrect). The presence of the arrow leads the user to think that the column is sortable, and that the sort is not working.

Actual Results: The up/down sort arrow shows

Additional Information: See attached screenshots