[FIX] web_editor: fix commands in inline

Some commands from the powerBox command bar were not working
properly in the e-shop product "terms and conditions" section.

This was due to the isolation of Odoo fields
inside the odoo editor as a all.
Those fields do not always have an editable block element
to apply the command on.

We disable some commands that should not be apear in this context.

We also remove a redundant command (separator) in website pages.

task-2962067

closes odoo/odoo#107037

Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>