docs: improve descriptions

Co-authored-by: LenaLenaPan <120552185+LenaLenaPan@users.noreply.github.com>

lib-ee/emqx_ee_bridge/i18n/emqx_ee_bridge_kafka.conf

@@ -62,7 +62,7 @@ emqx_ee_bridge_kafka {
     mqtt_topic {
         desc {
             en: "MQTT topic or topic filter as data source (bridge input).  If rule action is used as data source, this config should be left empty, otherwise messages will be duplicated in Kafka."
-            zh: "指定源 MQTT 主题，若由规则动作指定数据源，则该配置应留空，否则消息会被重复发送到 Kafka。"
+            zh: "MQTT 主题数据源由桥接指定，或留空由规则动作指定。"
         }
         label {
             en: "Source MQTT Topic"