[FIX] mail: avoid marking hint as resolved before message list render

This change highlighted issues with the async behavior of `useUpdate`, which
was no longer necessary and therefore reverted.

This in turn highlighted issue with animation of chat window unfolding, making
restoring of scroll position not work as intended due to the message list not
having its whole height available during some time after render. This animation
being minor (and even annoying in some cases) it was decided to remove it.

task-2387729

closes odoo/odoo#61881

Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>