Update list of automated branches

Author: sjohnr

RELEASE.adoc

@@ -59,9 +59,9 @@ The scheduled release process currently runs every Monday but only releases when
 The automated release process occurs on the following branches:
 
 * `main`
+* `6.0.x`
 * `5.8.x`
 * `5.7.x`
-* `5.6.x`
 
 For each of the above branches, the automated process performs the following checks before proceeding with the release: