Laravel upgrade doesn't work

I upgrade laravel to 5.4 from 5.3.

In composer.json i have :

 {
        "name" : "laravel/laravel",
        "description" : "The Laravel Framework.",
        "keywords" : [
            "framework",
            "laravel"
        ],
        "license" : "MIT",
        "type" : "project",
        "require" : {
            "php" : ">=5.6.4",
            "laravel/framework" : "5.4.*",
            "h4cc/wkhtmltopdf-amd64" : "0.12.x",
            "h4cc/wkhtmltoimage-amd64" : "0.12.x",
            "barryvdh/laravel-snappy" : "^0.3.3",
            "greggilbert/recaptcha" : "dev-master"
        },
        "require-dev" : {
            "fzaninotto/faker" : "~1.4",
            "mockery/mockery" : "0.9.*",
            "phpunit/phpunit" : "~5.7",
            "symfony/css-selector" : "2.8.*|3.0.*",
            "symfony/dom-crawler" : "2.8.*|3.0.*",
            "barryvdh/laravel-ide-helper" : "^2.2",
            "guzzlehttp/guzzle" : "~6.0"
        },
        "autoload" : {
            "classmap" : [
                "database"
            ],
            "psr-4" : {
                "App\\" : "app/"
            }
        },
        "autoload-dev" : {
            "classmap" : [
                "tests/TestCase.php"
            ]
        },
        "scripts" : {
            "post-root-package-install" : "php -r \"copy('.env.example', '.env');\"",
            "post-create-project-cmd" : "php artisan key:generate",
            "post-install-cmd" : [
                "Illuminate\\Foundation\\ComposerScripts::postInstall",
                "php artisan optimize"
            ],
            "post-update-cmd" : [
                "Illuminate\\Foundation\\ComposerScripts::postUpdate",
                "php artisan optimize"
            ]
        },
        "config" : {
            "preferred-install" : "dist"
        }
    }

I ran :

composer update

It seems to be ok :

composer update
Loading composer repositories with package information
Updating dependencies (including require-dev)
Package operations: 0 installs, 0 updates, 0 removals
Generating autoload files
> Illuminate\Foundation\ComposerScripts::postUpdate
> php artisan optimize
Generating optimized class loader
The compiled class file has been removed.

but when i ran this command : php artisan --version

the output is : Laravel Framework version 5.3.31

What's wrong ?

Thank's in advance for any help.

via Chebli Mohamed