chat_archiver: Fix misconfiguration where MAX_SERVER_LAG < MAX_DELAY

This leads to delayed JOIN/PARTs not being put in their proper batch
as it's already been closed. In fact, since each message is re-opening a batch from
more than MAX_SERVER_LAG seconds ago, each message becomes one batch.

chat_archiver/chat_archiver/main.py

@@ -47,8 +47,9 @@ COMMANDS = DELAYED_COMMANDS + [
 ]
 
 # Assume we're never more than this amount of time behind the server time
-# Worst case if too low: multiple output files for same batch that need merging later
-MAX_SERVER_LAG = 30
+# Worst case if too low: multiple output files for same batch that need merging later.
+# Should be greater than MAX_DELAY.
+MAX_SERVER_LAG = 60
 
 # When guessing when a non-timestamped event occurred, pad the possible range
 # by up to this amount before and after our best guess