[docs] Update 8.4.1 Release notes

remove information about JDG-5978 from the release notes. JDG-5978 will be available in 8.5
https://issues.redhat.com/browse/ISPN-13911 incorrectly tagged as a blocker for https://issues.redhat.com/browse/JDG-5252

the prints uploaded into JDG-5252 seems to be using the information provided by /rest/v2/caches/{name}?action=distribution

Pedro Ruivo: /rest/v2/caches/{name}?action=distribution exists in 8.4.x and it is the cache distribution. Returns a list of nodes and its information about the number of entries and memory

Pedro Ruivo: /rest/v2/caches/{cacheName}/{cacheKey}?action=distribution is new (does not exist in 8.4.x) and it the key distribution, in other words, which nodes has a copy of the key

Pedro Ruivo: No idea which one the console is using

Pedro Ruivo: the prints uploaded into JDG-5252 seems to be using the information provided by /rest/v2/caches/{name}?action=distribution