[FIX] website_blog: fix url in rss
[FIX] website_blog: fix url in rss

post.website_url contains the heading /.
Old code generate 404 url (https://www.odoo.com//blog/1/post/294)

ygol/odoo,dfang/odoo,bplancher/odoo,bplancher/odoo,hip-odoo/odoo,storm-computers/odoo,hip-odoo/odoo,laslabs/odoo,hip-odoo/odoo,Elico-Corp/odoo_OCB,dfang/odoo,laslabs/odoo,Elico-Corp/odoo_OCB,bplancher/odoo,microcom/odoo,ygol/odoo,laslabs/odoo,ygol/odoo,ygol/odoo,hip-odoo/odoo,hip-odoo/odoo,dfang/odoo,Elico-Corp/odoo_OCB,ygol/odoo,storm-computers/odoo,laslabs/odoo,hip-odoo/odoo,microcom/odoo,bplancher/odoo,laslabs/odoo,ygol/odoo,bplancher/odoo,ygol/odoo,microcom/odoo,dfang/odoo,storm-computers/odoo,dfang/odoo,microcom/odoo,dfang/odoo,laslabs/odoo,storm-computers/odoo,Elico-Corp/odoo_OCB,bplancher/odoo,Elico-Corp/odoo_OCB,microcom/odoo,microcom/odoo,Elico-Corp/odoo_OCB,storm-computers/odoo,storm-computers/odoo