Update CHANGELOG again for libaom v3.9.1

Bug: aomedia:3577
Change-Id: I21a59d9acd4aab37a8abd81def5952ab9eac7a14

CHANGELOG

diff --git a/CHANGELOG b/CHANGELOG
index 215e176..11d56ec 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,4 +1,4 @@
-2024-05-30 v3.9.1
+2024-06-03 v3.9.1
   This release includes several bug fixes. This release is ABI
   compatible with the last release. See
   https://aomedia.googlesource.com/aom/+log/v3.9.0..v3.9.1 for all the
@@ -14,6 +14,8 @@
       svc/scale controls (CVE-2024-5493)
     * aomedia:3571: {,highbd_}intrapred_neon.c: Avoid over-reads in z1
       and z3 preds
+    * aomedia:3578: libaom-3.9.0 undefined reference to
+      `aom_sub_pixel_variance16xh_ssse3'
     * oss-fuzz:68774: libaom:av1_dec_fuzzer: Segv on unknown address in
       od_ec_dec_init
     * Arm SVE build fixes.