test_support_views: Fix event_time of LicenseLedger entry created.

While creating a LicenseLedger entry in 'create_customer_and_plan',
we should set the 'event_time' to the same time at which the plan
is created.

Earlier, the 'event_time' for ledger entry & 'billing_cycle_anchor'
of the plan were set to different values, which is not the
correct behavior.

corporate/tests/test_support_views.py

@@ -662,7 +662,7 @@ class TestSupportEndpoint(ZulipTestCase):
         LicenseLedger.objects.create(
             licenses=10,
             licenses_at_next_renewal=10,
-            event_time=timezone_now(),
+            event_time=now,
             is_renewal=True,
             plan=plan,
         )