Bump symfony/yaml from 4.2.1 to 4.3.3

Bumps [symfony/yaml](https://github.com/symfony/yaml) from 4.2.1 to 4.3.3.
- [Release notes](https://github.com/symfony/yaml/releases)
- [Changelog](https://github.com/symfony/yaml/blob/master/CHANGELOG.md)
- [Commits](https://github.com/symfony/yaml/compare/v4.2.1...v4.3.3)

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

composer.json

@@ -12,7 +12,7 @@
         "symfony/flex": "^1.1",
         "symfony/framework-bundle": "4.2.*",
         "symfony/orm-pack": "^1.0",
-        "symfony/yaml": "4.2.*",
+        "symfony/yaml": "4.3.*",
         "tightenco/collect": "^5.7"
     },
     "config": {