I don’t think that particular text can be selected with css, so try making all the text in the cell transparent, then reverting the currency symbol and price to their normal colour. The text is still there and makes the cell appear too wide, hence the need to limit cell width.

.woocommerce-orders-table__cell-order-total {
  width:150px;
  color:rgba(0, 0, 0, 0);
}
.woocommerce-Price-amount {
  color:rgba(0, 0, 0, 1);
}

Custom css can be entered at:
Dashboard > Appearance > Customise > Additional CSS

If it doesn’t work for you, it may be because your theme’s markup is different, in which case please post the url for your site.