Fix faulty test. June has 30 days, so the test would fail when ran on…

… 31st in whatever the github timezone in. (once in a few months)

tests/events/models/test_event.py

@@ -59,7 +59,7 @@ def test_semester_with_month_lt_7_returns_spring(self):
         time = datetime.datetime(
             year=current_time.year,
             month=6,
-            day=current_time.day,
+            day=15,
         )
         self.event.start_time = time