Change v3.1.1 release date to 2021-06-08

BUG=aomedia:3056

Change-Id: I0fe83cd6ea2a7b48294db3579b985e5ba6c80995

CHANGELOG

diff --git a/CHANGELOG b/CHANGELOG
index 76d813d..dddef98 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,4 +1,4 @@
-2021-06-03 v3.1.1
+2021-06-08 v3.1.1
   This release includes several bug fixes.
 
   - Bug fixes: