notifications: Change sender arg of send_future_email to from_email.

This commit is a step towards the goal of replacing most of the
send_future_email pathway with a call to send_email.

Note that this commit changes the default value of sender from "Zulip
<NOREPLY_EMAIL_ADDRESS>" to "NOREPLY_EMAIL_ADDRESS". NOREPLY_EMAIL_ADDRESS
will soon be changed to have the Zulip in front.

zerver/worker/queue_processors.py

@@ -166,7 +166,7 @@ class ConfirmationEmailWorker(QueueProcessingWorker):
         send_future_email(
             "zerver/emails/invitation_reminder",
             [{'email': data["email"], 'name': ""}],
-            sender={'email': settings.ZULIP_ADMINISTRATOR, 'name': 'Zulip'},
+            from_email=settings.ZULIP_ADMINISTRATOR,
             context=context,
             delay=datetime.timedelta(days=2),
             tags=["invitation-reminders"])