[FIX] web_editor: use valid bootstrap for m2o editor options
[FIX] web_editor: use valid bootstrap for m2o editor options

The .dropdown is in a .btn-group environment while a .btn-group can
only contain .btn or .btn-group elements.

This induced problems where the m2o options covers the full overlay
environment, preventing clicks on the customize dropdown.

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