Deleting a share class is as easy as following the steps listed below:
Navigate to the entity for which you would like to delete a share class;
Go to the Governance > Share Classes section;
Select the share class you would like to delete - the share class details window will pop up;
Select Alter Class in the bottom righthand corner;
Select Remove Class at the very bottom of the list - this will set your share class to inactive;
In the share class record, move your cursor to the end of the record and select Delete;
Click Confirm in the pop-up window.