bump async_repl lib after changes (#656)

Author: paulomach

lib/charms/mysql/v0/async_replication.py

@@ -54,7 +54,7 @@
 # The unique Charmhub library identifier, never change it
 LIBID = "4de21f1a022c4e2c87ac8e672ec16f6a"
 LIBAPI = 0
-LIBPATCH = 7
+LIBPATCH = 8
 
 RELATION_OFFER = "replication-offer"
 RELATION_CONSUMER = "replication"