[DOCS] Updates release notes

Author: picandocodigo

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 7.17.9
+
+-  Backports fix from `elastic-transport`: [#66](https://github.com/elastic/elastic-transport-ruby/issues/66) - Manticore transport unable to send custom headers with `perform_request` [Pull Request](https://github.com/elastic/elastic-transport-ruby/pull/69).
+
 ## 7.17.8
 
 - Patch releases back to being detached from Elastic stack releases.

docs/release_notes/717.asciidoc

@@ -1,6 +1,12 @@
 [[release_notes_717]]
 === 7.17 Release notes
 
+[discrete]
+[[release_notes_7179]]
+=== 7.17.9 Release notes
+
+-  Backports fix from `elastic-transport`, fixes https://github.com/elastic/elastic-transport-ruby/issues/66[#66]: Manticore transport unable to send custom headers with `perform_request` https://github.com/elastic/elastic-transport-ruby/pull/69[Pull Request].
+
 [discrete]
 [[release_notes_7178]]
 === 7.17.8 Release notes