[skip ci]Add comment for NewRegisterPolicy (#10132)

Signed-off-by: sunby <bingyi.sun@zilliz.com>

internal/datacoord/channel_manager_factory.go

@@ -76,6 +76,7 @@ func NewConsistentHashChannelPolicyFactory(hashring *consistent.Consistent) *Con
 	}
 }
 
+// NewRegisterPolicy create a new register policy
 func (f *ConsistentHashChannelPolicyFactory) NewRegisterPolicy() RegisterPolicy {
 	return ConsistentHashRegisterPolicy(f.hashring)
 }