[IMP] calendar: update calendar_event_menu sequence to prevent shift

The sequence is equal to 10 and it is causing issues during upgrade. The order used by the menus is _order = sequence, id

As the menu has a new xmlid, it will be placed after the existing one because if his sequence. We could

1) lower the sequence value
2) don't provide a sequence (menuitem is noupdate False) and update the value in the upgrade script.

Proposal 1 is chosen as it does not require an upgrade script.

closes odoo/odoo#144716

Taskid: 3618126
Signed-off-by: Arnaud Joset (arj) <arj@odoo.com>

addons/calendar/views/calendar_views.xml

@@ -487,7 +487,7 @@
     <menuitem
         id="calendar_event_menu"
         name="Calendar"
-        sequence="10"
+        sequence="1"
         action="action_calendar_event"
         parent="mail_menu_calendar"
         groups="base.group_user"/>