There is no way to modify only that line of code through inheritance, but you can override name doing this on your own module:

class sale_order_line(osv.osv)
    _inherit='sale.order.line'

def product_id_change(self, cr, uid, ids, pricelist, product, qty=0,
        uom=False, qty_uos=0, uos=False, name='', partner_id=False,
        lang=False, update_tax=True, date_order=False, packaging=False, fiscal_position=False, flag=False, context=None):

    res=super(sale_order_line, self).product_id_change(cr, uid, ids, pricelist, product, qty=qty,
        uom=uom, qty_uos=qty_uos, uos=uos, name=name, partner_id=partner_id,
        lang=lang, update_tax=update_tax, date_order=date_order, packaging=packaging, fiscal_position=fiscal_position, flag=flag, context=context)

    #Above lines are going to call the native function and 'res' is going to store the result, so you can change the value right there

    if not flag:
        res['value']['name'] = self.pool.get('product.product').name_get(cr, uid, [product_obj.id], context=context_partner)[0][1]
        if product_obj.description_sale:
            res['value']['name'] += product_obj.description_sale

    return res

Well I'm just doing the code that you've modified. But functions can be inherited like this.

Hope that this can help you

im trying this module in v8, but dont work for me.

These are the different components of the simple module and their code:

Code in __init__.py:

import ti_order_lines_description

Code in __openerp__.py:

{
    "name": 'Modifications for XXX',
    "version": '1.0',
    "description": """XXX""",
    "author": 'XXX',
    "website": 'XXX',
    "depends": [
        'base',
        'sale',
    ],
    "demo": [],
    "data": [],
    "installable": True,
    "active": True,
    "category" : "",
}

Code in ti_modifications.py:

from openerp.osv import fields, osv
from tools.translate import _


###Fix: Remove "Product Name" from Sale Order product lines

class sale_order_line(osv.osv):
    _inherit='sale.order.line'

def product_id_change(self, cr, uid, ids, pricelist, product, qty=0,
        uom=False, qty_uos=0, uos=False, name='', partner_id=False,
        lang=False, update_tax=True, date_order=False, packaging=False, fiscal_position=False, flag=False, context=None):

    res=super(sale_order_line, self).product_id_change(cr, uid, ids, pricelist, product, qty=qty,
        uom=uom, qty_uos=qty_uos, uos=uos, name=name, partner_id=partner_id,
        lang=lang, update_tax=update_tax, date_order=date_order, packaging=packaging, fiscal_position=fiscal_position, flag=flag, context=context)
   #Above lines are going to call the native function and 'res' is going to store the result, so you can change the value right there

    if not flag:
        res['value']['name'] = self.pool.get('product.product').name_get(cr, uid, [product_obj.id], context=context_partner)[0][1]
        if product_obj.description_sale:
            res['value']['name'] = product_obj.description_sale
    return res
sale_order_line()

 make the "Description" (name) field in Sale Order lines to only show the products "Sales Description"(description_sale)....and NOT the products "Name"+"Sales Description" as per default. I think this code can help you.

from openerp.osv import osv, fields
from openerp.tools.translate import _

class sale_order_line(osv.Model):
    _name = 'sale.order.line'
    _inherit ='sale.order.line'

    def product_id_change(self, cr, uid, ids, pricelist, product, qty=0, uom=False, qty_uos=0, uos=False, name='', partner_id=False, lang=False, update_tax=True,
            date_order=False, packaging=False, fiscal_position=False, flag=False, context=None):
            
        product_obj = self.pool.get('product.product')
        partner_obj = self.pool.get('res.partner')
        partner = partner_obj.browse(cr, uid, partner_id)
        lang = partner.lang
        context_partner = {'lang': lang, 'partner_id': partner_id}
        
        res=super(sale_order_line, self).product_id_change(cr, uid, ids, pricelist, product, qty=qty, uom=uom, qty_uos=qty_uos, uos=uos, name=name,
            partner_id=partner_id, lang=lang, update_tax=update_tax, date_order=date_order, packaging=packaging, fiscal_position=fiscal_position, flag=flag, context=context)

        #Above lines are going to call the native function and 'res' is going to store the result, so you can change the value right there
        

        product_obj = product_obj.browse(cr, uid, product, context=context_partner)
        
        if not flag:
            res['value']['name'] = self.pool.get('product.product').name_get(cr, uid, [product_obj.id], context=context_partner)[0][1]
            if product_obj.description_sale:
                res['value']['name'] = product_obj.description_sale
        
        return res
    
sale_order_line()