[FIX] calendar: recurring events can have 0 repetitions

Steps to reproduce:
- install calendar
- create a recurring event with 0 repetitions
- save

Previous behavior:
raises an UserError, this would interrupt the sync with google calendar
Google calendar sometimes sets recurring events to 0 repetitions
once they are done recurring

Current behavior:
the event is handled like a punctual event but remains recurrent

initial commit: https://github.com/odoo/odoo/commit/ba727e15d2dc9a1325cd20527e2ccfe6f8bc63f0


opw-2185699

closes odoo/odoo#45920

X-original-commit: 2d5d496c
Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>