Ensure void return type translates to null

Author: WyriHaximus

Makefile

@@ -46,14 +46,11 @@ cs: ## Check the code for code style issues
 stan: ## Run static analysis (PHPStan)
 	$(DOCKER_RUN) vendor/bin/phpstan analyse src --ansi -c ./etc/qa/phpstan.neon
 
-psalm: ## Run static analysis (Psalm)
-	$(DOCKER_RUN) vendor/bin/psalm --threads=$(THREADS) --shepherd --stats --config=./etc/qa/psalm.xml
-
 composer-require-checker: ## Ensure we require every package used in this package directly
 	$(DOCKER_RUN) vendor/bin/composer-require-checker --ignore-parse-errors --ansi -vvv --config-file=./etc/qa/composer-require-checker.json
 
 composer-unused: ## Ensure we don't require any package we don't use in this package directly
-	$(DOCKER_RUN) vendor/bin/composer-unused --ansi
+	$(DOCKER_RUN) vendor/bin/composer-unused --ansi --configuration=./etc/qa/composer-unused.php
 
 composer-install: ## Install dependencies
 	$(DOCKER_RUN) composer install --no-progress --ansi --no-interaction --prefer-dist -o

composer.json

@@ -13,14 +13,13 @@
         "php": "^8.1",
         "ext-parallel": "*",
         "moneyphp/money": "^3.2.1 || ^4.0.0",
-        "react-parallel/contracts": "^2@dev",
-        "react-parallel/event-loop": "^2@dev",
+        "react-parallel/contracts": "^2.0.0",
+        "react-parallel/event-loop": "^2.0.0",
         "react/event-loop": "^1.5",
         "react/promise": "^2.9 || ^3.1",
         "wyrihaximus/async-test-utilities": "^5 || ^7.2",
         "wyrihaximus/pool-info": "^1.1 || ^2.0"
     },
-    "require-dev": {},
     "autoload": {
         "psr-4": {
             "ReactParallel\\Tests\\": "src/"