build-support/php: remove obsolete autoloader-suffix

Since https://github.com/composer/composer/pull/11663, the composer output is stable and reproducible, therefore, that prefix is now obsolete.

pkgs/build-support/php/pkgs/composer-local-repo-plugin.nix

···
 
     composer global config --quiet minimum-stability dev
     composer global config --quiet prefer-stable true
-    composer global config --quiet autoloader-suffix "nixPredictableAutoloaderSuffix"
     composer global config --quiet apcu-autoloader false
     composer global config --quiet allow-plugins.nix-community/composer-local-repo-plugin true
     composer global config --quiet repo.packagist false