VOL-2828 Bump version for 2.3 release

Change-Id: I353f6e4af2344d7d6082b7389b8da7b4b0faca29
diff --git a/VERSION b/VERSION
index 19013e6..3b31fa0 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.3.21-dev
+2.3.21