GH Actions: Bump phpcsstandards/xmllint-validate from 1.0.1 to 2.0.0 #853

Job	Run time
Basic CS and QA checks	34s
XML Code style	13s
phpstan / PHPStan	15s
Lint Markdown / Lint Markdown	7s
QA Markdown / QA Markdown	34s
Lint Yaml / Check GHA workflows	9s
Lint Yaml / Lint Yaml	5s
	1m 57s

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