Fix matrix-dendrite-create-account usage help

roles/matrix-dendrite/templates/dendrite/usr-local-bin/matrix-dendrite-create-account.j2

@@ -2,7 +2,7 @@
 #!/bin/bash
 
 if [ $# -ne 2 ]; then
-	echo "Usage: "$0" <username> <password>"
+	echo "Usage: "$0" <username> <password> <admin access: 0 or 1>"
 	exit 1
 fi