[FIX] calendar: note on meeting planned activity lack new line

- In a res.partner;
- Schedule activity;
- Choose 'meeting' as activity;
- Set a summary : 'test summary';
- Open Calendar;
- Chose a date and an hour;
- Edit the meeting;
- Add a description with a line break;
- Save the meeting;
- open the res.partner view;

Before this commit, the note on the planned activity lack the line
break.

Now, the note in the planned activity has the same output as the
description of the calendar meeting.

opw-2236838

closes odoo/odoo#50143

Signed-off-by: Jorge Pinna Puissant (jpp) <jpp@odoo.com>