Add some missing return types to internal/final classes

Author: nicolas-grekas

Pipes/UnixPipes.php

@@ -35,10 +35,7 @@ public function __construct(?bool $ttyMode, bool $ptyMode, $input, bool $haveRea
         parent::__construct($input);
     }
 
-    /**
-     * @return array
-     */
-    public function __sleep()
+    public function __sleep(): array
     {
         throw new \BadMethodCallException('Cannot serialize '.__CLASS__);
     }

Pipes/WindowsPipes.php

@@ -88,10 +88,7 @@ public function __construct($input, bool $haveReadSupport)
         parent::__construct($input);
     }
 
-    /**
-     * @return array
-     */
-    public function __sleep()
+    public function __sleep(): array
     {
         throw new \BadMethodCallException('Cannot serialize '.__CLASS__);
     }