Broken layout of title of tab

Hi!

Would you mind to please fix the layout of product tab?
A span tag is missing.

I was not able to find a GitHub repository to create a PR.
So here is the fix:

Line 589:
echo '<li class="bulkdiscount_tab bulkdiscount_options"><a href="#bulkdiscount_product_data" ' . $style . '><span>' . __( 'Bulk Discount', 'wc_bulk_discount' ) . '</span></a></li>';