Failing import of php-font-lib with composer and autoload

When composer is used to get dompdf, php-font-lib is dumped as dependency to phenx/php-font-lib in vendor folder; the git submodule in dompdf/lib is not initialized, so the require directive fails.
But the composer autoload mechanism does not need this import, cause all classes are already mapped (see the composer.json from php-font-lib), so, IMHO, we can safely remove it.