Revert "minor #32054 Prepare for PHP 7.4 preload (nicolas-grekas)"

This reverts commit a0aa94114a7b0334f94eb53c7536c729c1be2fef, reversing
changes made to 8496003634906d220ee1bc95f1547ced64545ffa.

Author: nicolas-grekas

DependencyInjection/CompatibilityServiceSubscriberInterface.contracts.php

@@ -12,9 +12,20 @@
 namespace Symfony\Bundle\FrameworkBundle\DependencyInjection;
 
 use Symfony\Component\DependencyInjection\ServiceSubscriberInterface as LegacyServiceSubscriberInterface;
+use Symfony\Contracts\Service\ServiceSubscriberInterface;
 
 if (interface_exists(LegacyServiceSubscriberInterface::class)) {
-    require __DIR__.\DIRECTORY_SEPARATOR.'CompatibilityServiceSubscriberInterface.legacy.php';
+    /**
+     * @internal
+     */
+    interface CompatibilityServiceSubscriberInterface extends LegacyServiceSubscriberInterface
+    {
+    }
 } else {
-    require __DIR__.\DIRECTORY_SEPARATOR.'CompatibilityServiceSubscriberInterface.contracts.php';
+    /**
+     * @internal
+     */
+    interface CompatibilityServiceSubscriberInterface extends ServiceSubscriberInterface
+    {
+    }
 }