Simplify subject line of partner reports so that they get bundled in …

…Gmail

donation/emails/partner_charity_report.py

@@ -127,7 +127,7 @@ def send_partner_charity_reports(test=True):
             cc = []
             body = "Hi team, here's the internal report for {0} from {1} to {2}".format(partner, start.strftime('%d-%m-%Y'), end.strftime('%d-%m-%Y'))
             message = EmailMessage(
-                subject="Internal report for {0} from {1} to {2}".format(partner, start.strftime('%d-%m-%Y'), end.strftime('%d-%m-%Y')),
+                subject="Effective Altruism Australia donation report [internal]",
                 body=body,
                 to=to if not test else [settings.TESTING_EMAIL],
                 cc=cc if not test else [settings.TESTING_EMAIL],