Hi,
You have to make a translation override on the key: X_ITEMS_IN_STOCK like:
X_ITEMS_IN_STOCK=""
www.hikashop.com/support/faq.html#tran
If you still want to display this text in the product page, so you will have to edit the view "product / quantity" via the menu Display > Views and add an if condition around the line:
echo '<span class="hikashop_product_stock_count">'.JText::sprintf('X_ITEMS_IN_STOCK',$this->row->product_quantity).'<br/></span>';
Something like:
if(JRequest::getVar('layout','show') != 'listing'){
echo '<span class="hikashop_product_stock_count">'.JText::sprintf('X_ITEMS_IN_STOCK',$this->row->product_quantity).'<br/></span>';
}