Update phpunit to fix security advisory error (PKSA-z3gr-8qht-p93v)

Author: JanJakes

composer.json

@@ -20,7 +20,7 @@
 		"phpcompatibility/phpcompatibility-wp": "*",
 		"php-parallel-lint/php-parallel-lint": "^1.3",
 		"yoast/phpunit-polyfills": "2.0.0",
-		"phpunit/phpunit": "8.5.38"
+		"phpunit/phpunit": "8.5.52"
 	},
 	"config": {
 		"allow-plugins": {