Adding release-2.64.0-postrelease to protected branches in .asf.yaml

Author: liferoad

.asf.yaml

@@ -51,6 +51,7 @@ github:
 
   protected_branches:
     master: {}
+    release-2.64.0-postrelease: {}
     release-2.64: {}
     release-2.63.0-postrelease: {}
     release-2.63: {}