A space was missing in lang var for Notifications

(cherry picked from commit b503a90)

lang/ilias_en.lang

@@ -12787,7 +12787,7 @@ notifications_adm#:#osd_delay_desc#:#Delay of the visible presentation in millis
 notifications_adm#:#osd_error_presentation_time_too_small#:#The Presentation Time has to be at least than 1000 miliseconds.
 notifications_adm#:#osd_error_refresh_interval_smaller_than_delay_and_vanish_combined#:#The Refresh Interval has to be greater than the Presentation Time and the Presentation Delay combined.
 notifications_adm#:#osd_error_refresh_interval_too_small#:#The Refresh Interval has to be at least than 3000 miliseconds.
-notifications_adm#:#osd_interval#:#Refreshinterval
+notifications_adm#:#osd_interval#:#Refresh interval
 notifications_adm#:#osd_interval_desc#:#Polling interval for checking of new notifications in miliseconds. A lower number will notify the user more quickly but increases the number of requests the web server must handle.
 notifications_adm#:#osd_play_sound#:#Play a Sound
 notifications_adm#:#osd_play_sound_desc#:#Play a sound when receiving a new notficiation.