chore(deps): bump silex/silex from 1.2.3 to 2.2.4 in /tests/apps/php

Bumps [silex/silex](https://github.com/silexphp/Silex) from 1.2.3 to 2.2.4.
- [Release notes](https://github.com/silexphp/Silex/releases)
- [Changelog](https://github.com/silexphp/Silex/blob/master/doc/changelog.rst)
- [Commits](https://github.com/silexphp/Silex/compare/v1.2.3...v2.2.4)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

tests/apps/php/composer.json

@@ -4,7 +4,7 @@
   "require": {
     "monolog/monolog": "~1.7",
     "php": ">=5.5.9",
-    "silex/silex": "~1.1"
+    "silex/silex": "~2.2"
   },
   "require-dev": {
     "heroku/heroku-buildpack-php": "*"