[FIX] mail: date format

Use a date format in order to display the due date of an activity since
it is a date filed, not a datetime.

Closes #22614
opw-813736

addons/mail/static/src/js/activity.js

@@ -140,7 +140,8 @@ var Activity = AbstractActivityField.extend({
                     nbPlannedActivities: nbActivities.planned,
                     nbTodayActivities: nbActivities.today,
                     nbOverdueActivities: nbActivities.overdue,
-                    date_format: time.getLangDatetimeFormat(),
+                    date_format: time.getLangDateFormat(),
+                    datetime_format: time.getLangDatetimeFormat(),
                 }));
             } else {
                 self.$el.empty();

addons/mail/static/src/xml/activity.xml

@@ -40,7 +40,7 @@
                                     </dd>
                                     <dt>Created on</dt>
                                     <dd class="mb8">
-                                        <t t-esc="activity.create_date.format(date_format)"/>
+                                        <t t-esc="activity.create_date.format(datetime_format)"/>
                                     </dd>
                                     <dt>Assigned to</dt>
                                     <dd class="mb8">