chore: Translate transifex_input.json in da

97% of minimum 50% translated source file: 'transifex_input.json'
on 'da'.

Sync of partially translated files: 
untranslated content is included with an empty translation 
or source language content depending on file format

translations/frontend-app-learning/src/i18n/messages/da.json

@@ -447,7 +447,7 @@
   "learning.streakCelebration.streakDiscountMessage": "Du har låst op for en {percent} % rabat, når du kun opgraderer dette kursus i en begrænset periode.",
   "learning.streakcelebration.factoida": "Brugere, der lærer {streak_length} dage i træk {bolded_section}, end dem, der ikke gør.",
   "learning.streakcelebration.factoidb": "Brugere, der lærer {streak_length} dage i træk {bolded_section} kontra dem, der ikke gør.",
-  "learning.streakCelebration.streakCelebrationCouponEndDateMessage": "Ends {date}.",
-  "learning.loading.failure": "There was an error loading this course.",
-  "learning.loading": "Loading course page…"
+  "learning.streakCelebration.streakCelebrationCouponEndDateMessage": "Slutter {date}.",
+  "learning.loading.failure": "Der opstod en fejl under indlæsning af dette kursus.",
+  "learning.loading": "Indlæser kursusside..."
 }