[skip e2e] Add comment for datacoord/client.Client (#14029)

Signed-off-by: Nshaoyue.chen <shaoyue.chen@zilliz.com>

internal/distributed/datacoord/client/client.go

@@ -94,6 +94,7 @@ func (c *Client) Start() error {
 	return nil
 }
 
+// Stop stops the client
 func (c *Client) Stop() error {
 	return c.grpcClient.Close()
 }