Replace deprecated @PHPUnit60Migration rule set

Author: XWB

.php-cs-fixer.php

@@ -14,7 +14,7 @@
         '@Symfony' => true,
         '@Symfony:risky' => true,
         '@PHP7x1Migration' => true,
-        '@PHPUnit60Migration:risky' => true,
+        '@PHPUnit6x0Migration:risky' => true,
         'combine_consecutive_issets' => true,
         'combine_consecutive_unsets' => true,
         'heredoc_to_nowdoc' => false,