[FIX] web: show event date/duration on mobile

Issue:
    - when you go inside a calendar event on mobile,
    you can't see its time and duration

Steps To Reproduce:
    - In mobile view, go to calendar and create an event.
    - Click on the event and notice you can't see it's time and duration.

Solution:
   - We were unable to view the date time, and duration because,
     in the `computeDateTimeAndDuration` function, the record's
     `isTimeHidden` attribute is set to True.
    - This was set in the `normalizeRecord` function, where we return
     'isTimeHidden: isTimeHidden || !showTime'.
    - To resolve this issue we take into account `isSmall` in the
     `showTime` boolean to ensure it functions correctly on mobile
     devices.

opw-3829004

addons/web/static/src/views/calendar/calendar_model.js

@@ -515,7 +515,7 @@ export class CalendarModel extends Model {
 
         const showTime =
             !(fieldMapping.all_day && rawRecord[fieldMapping.all_day]) &&
-            scale === "month" &&
+            (scale === "month" || this.env.isSmall) &&
             startType !== "date" &&
             start.day === end.day;