[FIX] website_portal: bad xpath
[FIX] website_portal: bad xpath

"//div[@class='o_my_sidebar']" is not valid and fails when evaluated.
Could have been replaced by "//div[contains(string(@class),"o_my_sidebar")]" but
as needs a view modification, using an id is better for future inheritance.

Fixes #10279

ygol/odoo,laslabs/odoo,Elico-Corp/odoo_OCB,ygol/odoo,bplancher/odoo,microcom/odoo,storm-computers/odoo,storm-computers/odoo,laslabs/odoo,ygol/odoo,ygol/odoo,hip-odoo/odoo,hip-odoo/odoo,microcom/odoo,stephen144/odoo,stephen144/odoo,Elico-Corp/odoo_OCB,stephen144/odoo,stephen144/odoo,dfang/odoo,Elico-Corp/odoo_OCB,hip-odoo/odoo,stephen144/odoo,laslabs/odoo,ygol/odoo,dfang/odoo,ygol/odoo,microcom/odoo,bplancher/odoo,microcom/odoo,microcom/odoo,bplancher/odoo,storm-computers/odoo,sysadminmatmoz/OCB,sysadminmatmoz/OCB,ygol/odoo,storm-computers/odoo,Elico-Corp/odoo_OCB,laslabs/odoo,bplancher/odoo,sysadminmatmoz/OCB,stephen144/odoo,sysadminmatmoz/OCB,Elico-Corp/odoo_OCB,bplancher/odoo,hip-odoo/odoo,dfang/odoo,hip-odoo/odoo,bplancher/odoo,hip-odoo/odoo,storm-computers/odoo,sysadminmatmoz/OCB,dfang/odoo,sysadminmatmoz/OCB,dfang/odoo,sysadminmatmoz/OCB,Elico-Corp/odoo_OCB,dfang/odoo,storm-computers/odoo,microcom/odoo,laslabs/odoo,laslabs/odoo