Update release-notes.asciidoc

Author: charlotte-hoblik

docs/reference/release-notes.asciidoc

@@ -12,7 +12,6 @@ This section summarizes the changes in each release.
 * <<release-notes-8.18.2>>
 * <<release-notes-8.18.1>>
 * <<release-notes-8.18.0>>
-* <<release-notes-8.17.9>>
 * <<release-notes-8.17.8>>
 * <<release-notes-8.17.7>>
 * <<release-notes-8.17.6>>
@@ -104,7 +103,6 @@ include::release-notes/8.18.3.asciidoc[]
 include::release-notes/8.18.2.asciidoc[]
 include::release-notes/8.18.1.asciidoc[]
 include::release-notes/8.18.0.asciidoc[]
-include::release-notes/8.17.9.asciidoc[]
 include::release-notes/8.17.8.asciidoc[]
 include::release-notes/8.17.7.asciidoc[]
 include::release-notes/8.17.6.asciidoc[]