keep the uppercase letter for flag info

Signed-off-by: yulng <wei.yang@daocloud.io>

cmd/ctr/commands/containers/checkpoint.go

@@ -33,15 +33,15 @@ var checkpointCommand = cli.Command{
 	Flags: []cli.Flag{
 		cli.BoolFlag{
 			Name:  "rw",
-			Usage: "include the rw layer in the checkpoint",
+			Usage: "Include the rw layer in the checkpoint",
 		},
 		cli.BoolFlag{
 			Name:  "image",
-			Usage: "include the image in the checkpoint",
+			Usage: "Include the image in the checkpoint",
 		},
 		cli.BoolFlag{
 			Name:  "task",
-			Usage: "checkpoint container task",
+			Usage: "Checkpoint container task",
 		},
 	},
 	Action: func(context *cli.Context) error {