remove unused import

competition/models.py

@@ -20,7 +20,7 @@
 from competition.exceptions import FreezingNotClosedResults
 from competition.querysets import ActiveQuerySet
 from competition.utils.school_year_manipulation import (
-    get_school_year_end_by_date, get_school_year_start_by_date)
+    get_school_year_end_by_date)
 from personal.models import Profile, School
 from user.models import User