[DX] Use Symfony "dark-mode"-responsive logo in README

Following symfony#53105 @javiereguiluz uploaded a Symfony "dynamic" logo, which color scheme depends on user preferences.

Thus allowing the README's logo to look sharper and cleaner in dark mode (on Github.com, on PHPStorm, ...)

```diff
<svg>
    <style>
        .symfony-logo-circle, .symfony-logo-letter { fill: #000; }
        .symfony-logo-circle-letters { fill: #fff; }
+        @media (prefers-color-scheme: dark) {
+            .symfony-logo-circle, .symfony-logo-letter { fill: #fff; }
+            .symfony-logo-circle-letters { fill: #000; }
        }
    </style>
    <!-- SVG code -->
</svg>
```

Author: smnandre

README.md

@@ -1,5 +1,5 @@
 <p align="center"><a href="https://symfony.com" target="_blank">
-    <img src="https://symfony.com/logos/symfony_black_02.svg">
+    <img src="https://symfony.com/logos/symfony_dynamic_01.svg" alt="Symfony Logo">
 </a></p>
 
 [Symfony][1] is a **PHP framework** for web and console applications and a set