Update usage description for fleetctl apply (#38131)

- To mirror the docs:
https://github.com/fleetdm/fleet/blob/main/docs/Contributing/guides/cli/fleetctl-apply.md

<img width="1102" height="148" alt="Screenshot 2026-01-09 at 4 15 19 PM"
src="https://github.com/user-attachments/assets/1b8bc5c4-312c-44ae-9fa3-b737b6795ad0"
/>

- Context: https://github.com/fleetdm/fleet/issues/38130

cmd/fleetctl/fleetctl/apply.go

@@ -20,7 +20,7 @@ func applyCommand() *cli.Command {
 	)
 	return &cli.Command{
 		Name:      "apply",
-		Usage:     "Apply files to declaratively manage osquery configurations",
+		Usage:     "Use for one-off imports and backwards compatibility GitOps",
 		UsageText: `fleetctl apply [options]`,
 		Flags: []cli.Flag{
 			&cli.StringFlag{