Fix version bump.

Signed-off-by: Oliver Chang <oliverchang@users.noreply.github.com>

Author: oliverchang

docs/schema.md

@@ -8,7 +8,7 @@ aside:
 show_edit_on_github: true
 ---
 
-**Version 1.6.4 (April 5, 2024)**
+**Version 1.6.3 (April 5, 2024)**
 
 Original authors:
 - Oliver Chang (ochang@google.com)