fix: install php-coveralls in ci

Signed-off-by: Vitor Mattos <vitor@php.rio>

Author: vitormattos

composer.json

@@ -30,6 +30,7 @@
         "phpunit/phpunit": "^11.0",
         "donatj/mock-webserver": "^2.7",
         "friendsofphp/php-cs-fixer": "^3.0",
+        "php-coveralls/php-coveralls": "^2.9",
         "vimeo/psalm": "^6.0"
     },
     "autoload": {