Clarify why the Gerrit v3.9.0-rc2 release has been skipped

Change-Id: I0d376170e5d927235bc3b5d9a37e5608ecb2818e
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 f40695d..4b37451 100644
--- a/_posts/2023-10-05-gerrit-3.9-release-plan.md
+++ b/_posts/2023-10-05-gerrit-3.9-release-plan.md
@@ -14,12 +14,17 @@
 | Date      | Activity                                           |
 |-----------|----------------------------------------------------|
 | Oct 20    | Create `stable-3.9` branch, Release `3.9.0-rc0`    |
-| Oct 27    | Release `3.9.0-rc1`                                |
-| Nov  3    | Release `3.9.0-rc2`                                |
-| Nov 10    | Release `3.9.0-rc3` - Feature freeze deadline      |
-| Nov 17    | Release `3.9.0-rc4`                                |
+| Oct 27    | Release `3.9.0-rc1` (*)                            |
+| 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    | Final release of `3.9.0`                           |
 
+> **NOTE**: The `3.9.0-rc2` release was not announced and limited to
+> the release of the [gerrit-acceptance-framework on Maven](https://repo1.maven.org/maven2/com/google/gerrit/gerrit-acceptance-framework/3.9.0-rc2/).
+> From a Gerrit's perspective, it was identical to the `3.9.0-rc1`
+> therefore did not make sense to have it officially released.
+
 ## Java 17
 
 The language level used for Gerrit source code will stay on Java 11,