Coding Standards: Update PHPCS Composer plugin to v0.6.0.

Release log: https://github.com/Dealerdirect/phpcodesniffer-composer-installer/releases/tag/v0.6.0

Props jrf.
See #49222.

git-svn-id: https://develop.svn.wordpress.org/trunk@47389 602fd350-edb4-49c9-b593-d223f7449a82

composer.json

@@ -13,7 +13,7 @@
 		"php": ">=5.6"
 	},
 	"require-dev": {
-		"dealerdirect/phpcodesniffer-composer-installer": "~0.5.0",
+		"dealerdirect/phpcodesniffer-composer-installer": "~0.6.0",
 		"wp-coding-standards/wpcs": "~2.1.0",
 		"phpcompatibility/phpcompatibility-wp": "^2.1.0"
 	},