[TASK] Remove dependency sebastian/diff

This package is not used in extension builder directly. This paves the way to use a newer version of this package and unlocks the usage of phpunit v9.

composer.json

@@ -30,7 +30,6 @@
 	"require-dev": {
 		"friendsofphp/php-cs-fixer": "^2.18",
 		"roave/security-advisories": "dev-latest",
-		"sebastian/diff": "^3.0",
 		"typo3/cms-frontend": "^11.4",
 		"typo3/cms-install": "^11.4",
 		"typo3/coding-standards": "^0.3.0",