Disable code sniffer until memory problem is fixed

See https://travis-ci.org/phpbb-de/phpbb-ext-movemessage/jobs/29771214#L716

phpBB/vendor/bin/phpcs -s --extensions=php --standard=build/code_sniffer/rules
et-php-extensions.xml '--ignore=phpBB/ext/phpbbde/movemessage/tests/*' '--igno
re=phpBB/ext/phpbbde/movemessage/vendor/*' phpBB/ext/phpbbde/movemessage

PHP Fatal error: Allowed memory size of 1073741824 bytes exhausted (tried to a
llocate 1068236755 bytes) in /home/travis/build/phpBB3/phpBB/vendor/squizlabs/
php_codesniffer/CodeSniffer/File.php on line 2606