XEP-0411: extend LC

Originally, I intended to extend the LC by two weeks on
2020-09-01. However, the email I sent regarding that did not pass
through the list server, so nobody noticed.

Here I’ll do the update on the XEP itself, too, and also send
another email.

xep-0411.xml

@@ -11,7 +11,7 @@
   &LEGALNOTICE;
   <number>0411</number>
   <status>Proposed</status>
-  <lastcall>2020-08-18</lastcall>
+  <lastcall>2020-10-14</lastcall>
   <type>Standards Track</type>
   <sig>Standards</sig>
   <approver>Council</approver>