The docs for deprecation notice resulting from this issue: https://issues.redhat.com/browse/LOG-4558 include a line about providing bug fixes and support for the deprecated feature.  We need to remove this line since this functionality was never implemented and actually does nothing.

Suggested change for 2nd bullet:  

In Logging 5.9, the Fields option for the Splunk output type was never implemented and is now deprecated. It will be removed in a future release.

Doc link:  
https://docs.openshift.com/container-platform/4.15/logging/logging_release_notes/logging-5-9-release-notes.html#logging-release-notes-5-9-0-deprecation-notice