CHASM: Fix default sharding function (#7214)

## What changed?
<!-- Describe what has changed in this PR -->
Fix default sharding function.

## Why?
<!-- Tell your future self why have you made these changes -->
Made a typo in my previous PR #7184.

chasm/ref.go

@@ -29,7 +29,7 @@ import (
 )
 
 var (
-	defaultShardingFn = func(key EntityKey) string { return key.NamespaceID + "_" + key.EntityID }
+	defaultShardingFn = func(key EntityKey) string { return key.NamespaceID + "_" + key.BusinessID }
 )
 
 type EntityKey struct {