CI: Fix AppVeyor integration

Author: keradus

.appveyor.yml

@@ -30,7 +30,7 @@ install:
     - echo extension=php_openssl.dll >> php.ini
     - echo extension=php_mbstring.dll >> php.ini
     - IF NOT EXIST C:\tools\composer.phar (cd C:\tools && appveyor DownloadFile https://getcomposer.org/composer-stable.phar)
-    - copy composer-stable.phar composer.phar
+    - rename C:\tools\composer-stable.phar composer.phar
     - cd C:\projects\php-cs-fixer
     - php C:\tools\composer.phar global show hirak/prestissimo -q || php C:\tools\composer.phar global require hirak/prestissimo