fix(instance): fix index out of range panic in warningServerTypeDeprecated

Author: frivoire

internal/namespaces/instance/v1/helpers_types.go

@@ -67,14 +67,14 @@ func warningServerTypeDeprecated(
 	server *instance.Server,
 ) []string {
 	warning := make([]string, 0, 2)
-	warning[0] = terminal.Style(
+	warning = append(warning, terminal.Style(
 		fmt.Sprintf(
 			"Warning: server type %q will soon reach EndOfService",
 			server.CommercialType,
 		),
 		color.Bold,
 		color.FgYellow,
-	)
+	))
 
 	eosDate, err := getEndOfServiceDate(ctx, client, server.Zone, server.CommercialType)
 	if err != nil {