[8.15](backport #41119) Add a known issue entry for 8.15.0 and 8.15.2 referencing https://github.com/elastic/beats/issues/41118

[8.15](backport #41119) Add a known issue entry for 8.15.0 and 8.15.2 referencing https://github.com/elastic/beats/issues/41118 #4794