These two rules were used to restrict livechat users
to the read access to their own messages,
and allow livechat managers to see all messages.
Since 9.0, livechat messages are no longer
`im.chat.message` records (8.0),
they are now `mail.message` records, and this model
already implements its own security rules.
See `check_access_rule` of `mail.message` to know
more about the access rules of this model.
Therefore, these security rules are no longer necessary in 9.0.
Besides, it had as side-effect to restrict the access of
livechat managers for `mail.message` records.
For instance,
livechat users were no longer able to create customers.
opw-651958
Denis Ledoux
30894d15b1