Use higher minimum version for phpunit bridge

Author: alcaeus

composer.json

@@ -17,7 +17,7 @@
     },
     "require-dev": {
         "squizlabs/php_codesniffer": "^3.5, <3.5.5",
-        "symfony/phpunit-bridge": "^4.4 || ^5.0"
+        "symfony/phpunit-bridge": "^5.2@beta"
     },
     "autoload": {
         "psr-4": { "MongoDB\\": "src/" },