main: list-images takes no args (just --filter)

Tiny commit to error if extra arguments are passed to list-images.
Only `--filter` is supported there currently.

cmd/image-builder/main.go

@@ -64,6 +64,7 @@ operating sytsems like centos and RHEL with easy customizations support.`,
 		Short:        "List buildable images, use --filter to limit further",
 		RunE:         cmdListImages,
 		SilenceUsage: true,
+		Args:         cobra.NoArgs,
 	}
 	listImagesCmd.Flags().StringArray("filter", nil, `Filter distributions by a specific criteria (e.g. "type:rhel*")`)
 	listImagesCmd.Flags().String("output", "", "Output in a specific format (text, json)")