[skip ci] Add comment for proxy (#10143)

Signed-off-by: dragondriver <jiquan.long@zilliz.com>

internal/proxy/impl.go

@@ -39,6 +39,7 @@ import (
 	"github.com/milvus-io/milvus/internal/util/typeutil"
 )
 
+// UpdateStateCode updates the state code of Proxy.
 func (node *Proxy) UpdateStateCode(code internalpb.StateCode) {
 	node.stateCode.Store(code)
 }