The Infopath form has published in the Sharepoint Form library . After published the promoted fields is added in the respective form library. You can not remove the column because it is read only.
Solution:
You can open Sharepoint Manager and Open the Web,Form Library and set the specific column Allow deletion to yes, Save and delete the column.
Solution:
You can open Sharepoint Manager and Open the Web,Form Library and set the specific column Allow deletion to yes, Save and delete the column.