Changing the wording to singular

Signed-off-by: Matthias Wessendorf <[email protected]>

Author: matzew

serverless/knative_eventing/serverless-kafka.adoc

@@ -48,7 +48,7 @@ spec:
 include::modules/serverless-install-kafka-odc.adoc[leveloffset=+2]
 
 [id="serverless-kafka-channel-link"]
-== Using Kafka channels
+== Using Kafka channel
 
 Create a xref:../../serverless/channels/serverless-creating-channels.adoc#serverless-creating-channels[Kafka channel].