Update mediawiki/mediawiki-codesniffer to 19.1.0 to fix php7.3 problem

[umherirrender]

mediawiki/mediawiki-codesniffer 19.1.0 was released to fix a php7.3 problem in the upstream phpcs, which stop the mediawiki CI to test all extensions against php7.3

Please update to require 19.1.0 and release a new wikibase codesniffer release 0.5.1 to get the php7.3 fix. After that the extension with wikibase codesniffer can get the update to the new version.

See https://phabricator.wikimedia.org/T207250 for more description about the problem

Thanks