How can I remove ALL sort arrows from ALL columns?

I am trying to remove all of the sort arrows from the column headers when 'orderable' is set to false.

I included the following code in my datatable definition but an arrow continues to appear on the first column. I am not allowing sorting on any column, rather I'm using filtering and I don't want the sort arrows showing up at all.

columnDefs: [{
"orderable": false,
"targets": '_all'
}