docs: add changelog for pr 13790

changes/ce/fix-13790.en.md

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+The default heartbeat interval for the MQTT connector has been reduced from 300 seconds to 160 seconds.
+
+This change helps maintain the underlying TCP connection by preventing timeouts due to the idle limits
+imposed by load balancers or firewalls, which typically range from 3 to 5 minutes depending on the cloud provider.
+