Add missing return types to tests/internal/final methods

Author: nicolas-grekas

CurlHttpClient.php

@@ -345,10 +345,7 @@ public function reset()
         $this->multi->reset();
     }
 
-    /**
-     * @return array
-     */
-    public function __sleep()
+    public function __sleep(): array
     {
         throw new \BadMethodCallException('Cannot serialize '.__CLASS__);
     }

HttplugClient.php

@@ -218,10 +218,7 @@ public function createUri($uri): UriInterface
         throw new \LogicException(sprintf('You cannot use "%s()" as the "nyholm/psr7" package is not installed. Try running "composer require nyholm/psr7".', __METHOD__));
     }
 
-    /**
-     * @return array
-     */
-    public function __sleep()
+    public function __sleep(): array
     {
         throw new \BadMethodCallException('Cannot serialize '.__CLASS__);
     }

Response/AmpResponse.php

@@ -142,10 +142,7 @@ public function getInfo(string $type = null)
         return null !== $type ? $this->info[$type] ?? null : $this->info;
     }
 
-    /**
-     * @return array
-     */
-    public function __sleep()
+    public function __sleep(): array
     {
         throw new \BadMethodCallException('Cannot serialize '.__CLASS__);
     }

Response/CommonResponseTrait.php

@@ -127,10 +127,7 @@ public function toStream(bool $throw = true)
         return $stream;
     }
 
-    /**
-     * @return array
-     */
-    public function __sleep()
+    public function __sleep(): array
     {
         throw new \BadMethodCallException('Cannot serialize '.__CLASS__);
     }