docs(changeset): Fix bug in PgSubscriber

Author: benjie

.changeset/itchy-dingos-repair.md

@@ -0,0 +1,8 @@
+---
+"@dataplan/pg": patch
+"graphile-build-pg": patch
+---
+
+Fix PgSubscriber: do NOT automatically re-establish subscriptions, instead
+terminate them so the clients know something went wrong and can invoke the
+relevant re-synchronization code.