Update 2.15.4 release notes

(for Change-Id Ic194642e427c60d89713bde913f992bafe3e811d)

Change-Id: Ia2511aa20352f7df67f531abd638a8b8771d3697
diff --git a/pages/site/releases/2.15.md b/pages/site/releases/2.15.md
index 8bfdb54..5c89606 100644
--- a/pages/site/releases/2.15.md
+++ b/pages/site/releases/2.15.md
@@ -485,6 +485,9 @@
 
   In some cases it was possible to attempt to reuse an already closed
   connection, which resulted in an internal server exception.
+* [Issue 9586](https://bugs.chromium.org/p/gerrit/issues/detail?id=9586) Reload
+  change page to land on the latest patch set after change submission in
+  PolyGerrit.
 * Upgrade JGit to 4.9.5.201809180939-r.
 
   * [Issue 9153](https://bugs.chromium.org/p/gerrit/issues/detail?id=9153):