Update monolog/monolog requirement from ^2.0 to ^3.0 (#228)

Updates the requirements on [monolog/monolog](https://github.com/Seldaek/monolog) to permit the latest version.
- [Release notes](https://github.com/Seldaek/monolog/releases)
- [Changelog](https://github.com/Seldaek/monolog/blob/main/CHANGELOG.md)
- [Commits](Seldaek/monolog@2.0.0...3.0.0)

---
updated-dependencies:
- dependency-name: monolog/monolog
  dependency-type: direct:development
...

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composer.json

@@ -87,7 +87,7 @@
         "ekino/phpstan-banned-code": "^1.0",
         "infection/infection": "dev-master",
         "matthiasnoback/symfony-dependency-injection-test": "^4.3",
-        "monolog/monolog": "^2.0",
+        "monolog/monolog": "^3.0",
         "php-http/curl-client": "^2.0",
         "php-http/mock-client": "^1.3",
         "phpstan/phpstan": "^1.0",