Undo wrong change in absence importer

CHANGELOG.rst

@@ -9,6 +9,11 @@ and this project adheres to `Semantic Versioning`_.
 Unreleased
 ----------
 
+Fixed
+~~~~~
+
+* Importer failed sometimes on progressing absences.
+
 `2.3.2`_ - 2022-09-01
 ---------------------
 

aleksis/apps/untis/util/mysql/importers/absences.py

@@ -183,6 +183,5 @@ def import_absences(
         if a.import_ref_untis and a.import_ref_untis not in existing_absences:
             logger.info("Absence {} deleted".format(a.id))
             a.delete()
-            LessonSubstitution.objects.filter(absence_ref_untis=a.import_ref_untis).delete()
 
     return ref, created_substitutions