Remove the unused dependency on composer/package-versions-deprecated

The ProxyManagerBridge depends on friendsofphp/proxy-manager-lts which
has an optional dependency on the PackageVersions class to implement the
`ProxyManager\Version::getVersion` method on composer 1 (with a fallback
to a less precise version number).
However, the bridge has stopped using that API in favor of feature
detection, so the dependency is unused.

src/Symfony/Bridge/ProxyManager/composer.json

@@ -17,7 +17,6 @@
     ],
     "require": {
         "php": ">=7.1.3",
-        "composer/package-versions-deprecated": "^1.8",
         "friendsofphp/proxy-manager-lts": "^1.0.2",
         "symfony/dependency-injection": "^4.0|^5.0",
         "symfony/polyfill-php80": "^1.16"