Use older version of Composer

PHP Fatal error:  During class fetch: Uncaught Declaration of Crate\PDO\PDOCrateDB::prepare(string $statement, array $options = Array) should be compatible with PDO::prepare($statement, $options = NULL)

.github/workflows/tests.yml

@@ -44,7 +44,7 @@ jobs:
         with:
           php-version: ${{ matrix.php-version }}
           # Select PHPUnit version suitable for PHP 7.2.
-          tools: composer, phpunit:^8.5
+          tools: composer:2.4.4, phpunit:^8.5
 
       - uses: ramsey/composer-install@v2