build: Updating mediawiki/mediawiki-codesniffer to 29.0.0
The following sniffs are failing and were disabled:
- MediaWiki.Commenting.FunctionComment.MissingReturn
Additional changes:
- Also sorted "composer fix" command to run phpcbf last.
- .gitignore: Added .phpunit.result.cache (T242727).
Change-Id: Ie01147209112055b00a38a2d54f45b6a3be51ec8