docs: add changelog

changes/ce/fix-10462.en.md

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+Deprecate config `broker.shared_dispatch_ack_enabled`.
+This was designed to avoid dispatching messages to a shared-subscription session which has the client disconnected.
+However since v5.0.9, this feature is no longer useful because the shared-subscrption messages in a expired session will be redispatched to other sessions in the group.
+See also: https://github.com/emqx/emqx/pull/9104