Merge pull request #8231 from dCache/docubot-edfe9a5

[skip-ci] docs: note removal of Kafka support from NFS door

Author: kofemann

docs/TheBook/src/main/markdown/kafkaproducer.md

@@ -51,18 +51,14 @@ Set kafka topic name
 dcache.kafka.topic = billing
 ```
 
-"billing" is default. The following service level variables
-reference dcache.kafka.topic:
+"billing" is default.
 
-   nfs.kafka.topic = ${dcache.kafka.topic}
-   pool.kafka.topic = ${dcache.kafka.topic}
-   webdav.kafka.topic = ${dcache.kafka.topic}
-   xrootd.kafka.topic = ${dcache.kafka.topic}
 
-Note that the FTP door no longer supports pushing messages to Kafka; the
-producer for FTP has been removed and any `ftp.kafka.*` properties are now
+**Note** that doors no longer supports pushing messages to Kafka; the
+producer for doors has been removed and any `nfs/ftp/webdav.kafka.*` properties are now
 obsolete.
 
+
 ### 3. Start Server
 
 ```console-root