Per the problem outlined in the below community post, it appears the API is unable to remove existing hyperlinks from cells. It is possible to add or update hyperlinks, but not delete/remove them.
Please add the ability to either completely clear cells (including hyperlinks) or remove just existing hyperlinks using the API. If this capability already exists, please update the online documentation to clearly demonstrate how to clear hyperlinks - my efforts (outlined in the community post) were all unsuccessful in accomplishing this task.