mention nifi reporting task regression

Author: maltesander

modules/ROOT/pages/release-notes.adoc

@@ -363,8 +363,11 @@ helm install --wait zookeeper-operator stackable-stable/zookeeper-operator --ver
 
 ==== Known upgrade issues
 
-> todo: mention JMX Exporter?
-> todo: do we mention NiFi 2.0.0 (experimental)? because NiFi 1.27.0 -> 2.0.0 requires manual intervention (basically same as in the 24.7 note)
+> todo: mention JMX Exporter? Malte: Its mentioned in the Monitoring section and not really an upgrade issue?
+
+* Apache NiFi: For the experimental NiFi version `2.0.0`, the `PrometheusReportingTask`, use to activate a Prometheus metrics endpoint, was removed. 
+  NiFi now has its own API to directly access metrics. In contrast to previous versions, the metrics endpoints now requires authentication which is
+  not supported by the Stackable operator for Apache NiFi in this release.
 
 == Release 24.7