Add more return types after fixing a typo in my script

Author: nicolas-grekas

Node/Specificity.php

@@ -53,10 +53,8 @@ public function getValue(): int
     /**
      * Returns -1 if the object specificity is lower than the argument,
      * 0 if they are equal, and 1 if the argument is lower.
-     *
-     * @return int
      */
-    public function compareTo(self $specificity)
+    public function compareTo(self $specificity): int
     {
         if ($this->a !== $specificity->a) {
             return $this->a > $specificity->a ? 1 : -1;