How to remove the project name column in sales invoice?

1.Sales invoice project name cannot be deleted.

2. The user needs to select the sales invoice created to  click the delete button.

3. Create a new sales invoice and go to MY Biztory custom back the  missing reference number on running number and save.

4. Create a new sales invoice and fill in the missing ref no and don't fill in the 'project name' > save.

5.  After created the invoice, please go to my biztory > sales > custom back the last ref (sale) running number > save