chore: add changelog for mqtt.max_awaiting_rel

changes/ce/fix-10055.en.md

@@ -0,0 +1 @@
+Fix `mqtt.max_awaiting_rel` change does not work.

changes/ce/fix-10055.zh.md

@@ -0,0 +1 @@
+修复 `mqtt.max_awaiting_rel` 更新不生效问题。