Update nette/tester requirement from 2.4.1 to 2.4.2

Updates the requirements on nette/tester to permit the latest version.

---
updated-dependencies:
- dependency-name: nette/tester
  dependency-type: direct:development
...

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

composer.json

@@ -19,7 +19,7 @@
         "nette/utils": "^3.2@dev"
     },
     "require-dev": {
-        "nette/tester": "2.4.1",
+        "nette/tester": "2.4.2",
         "phpstan/phpstan": "1.5.3",
         "phpstan/phpstan-strict-rules": "1.1.0",
         "phpstan/phpstan-nette": "1.0.0",