How to remove a field from a Table

i want to remove Post field from HashTag table but getting error .

as the error message says, you cannot remove a field or change its type currently.
If you no longer want to use the field, you can ignore it but you must add a field with a different name if you want to change its type.

We are working on making it possible to change the types of fields in a future version which will also allow you to migrate data from the old type to the new one. This is not yet supported.