Re-add line for broken 3.9.0 release

It's better to be clear that 3.9.0 was released but is a broken release.

Change-Id: Iaa8f4317b5e38d5e7596db8a7f1b61f906d31c80

_posts/2023-10-05-gerrit-3.9-release-plan.md

diff --git a/_posts/2023-10-05-gerrit-3.9-release-plan.md b/_posts/2023-10-05-gerrit-3.9-release-plan.md
index ba9de45..7519ecd 100644
--- a/_posts/2023-10-05-gerrit-3.9-release-plan.md
+++ b/_posts/2023-10-05-gerrit-3.9-release-plan.md
@@ -18,6 +18,7 @@
 | Nov  3    | Release `3.9.0-rc3`                                |
 | Nov 10    | Release `3.9.0-rc4` - Feature freeze deadline      |
 | Nov 17    | Release `3.9.0-rc5`                                |
+| Nov 24    | Release of `3.9.0` **BROKEN** (**)                 |
 | Nov 28    | Release `3.9.0-rc6` (**)                           |
 | Dec  1    | Final release of `3.9.0.1`                         |