The `test_complete_chatbot_flow_ui` ensures it is possible to add
reactions to the chat bot messages once the thread is saved on the
server.
This test was sometimes failing because the condition that is used to
wait for the thread to be persisted is incorrect: it checks that a
message with the user response exists but the chat bot question also
contains the response text.
This PR fixes the issue by using the `contains` helper instead: it
will wait until the expected state is reached.
fixes runbot-55291
closesodoo/odoo#151720
Signed-off-by: Didier Debondt (did) <did@odoo.com>