Merge 5.13 release notes

Author: marcphilipp

documentation/src/docs/asciidoc/release-notes/index.adoc

@@ -19,14 +19,6 @@ include::{includedir}/link-attributes.adoc[]
 
 include::{basedir}/release-notes-5.13.0.adoc[]
 
-include::{basedir}/release-notes-5.13.0-RC1.adoc[]
-
-include::{basedir}/release-notes-5.13.0-M3.adoc[]
-
-include::{basedir}/release-notes-5.13.0-M2.adoc[]
-
-include::{basedir}/release-notes-5.13.0-M1.adoc[]
-
 include::{basedir}/release-notes-5.12.2.adoc[]
 
 include::{basedir}/release-notes-5.12.1.adoc[]