chore(i18n): Grammar improvement

Reported at Transifex

Signed-off-by: rakekniven <2069590+rakekniven@users.noreply.github.com>

Author: rakekniven

user_manual/groupware/calendar.rst

@@ -176,7 +176,7 @@ check and concretize the time span or set the event as an all-day event. Optiona
 you can specify a location and a description.
 
 If you want to edit advanced details such as the **Attendees** or **Reminders**, or if you
-want to set the event as a repeating-event, click on the ``More`` button to open the advanced editor.
+want to set the event as a repeating event, click on the ``More`` button to open the advanced editor.
 
 Add Talk conversation
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