Don't doubly include MessageTrait.

RequestTrait already includes MessageTrait. Also pin to newer diactoros
as there are problems with older versions.

Refs #10495

composer.json

@@ -24,7 +24,7 @@
         "cakephp/chronos": "~1.0",
         "aura/intl": "^3.0.0",
         "psr/log": "^1.0",
-        "zendframework/zend-diactoros": "~1.0"
+        "zendframework/zend-diactoros": "^1.4"
     },
     "suggest": {
         "ext-openssl": "To use Security::encrypt() or have secure CSRF token generation.",

src/Http/Client/Request.php

@@ -27,7 +27,6 @@ use Zend\Diactoros\Stream;
  */
 class Request extends Message implements RequestInterface
 {
-    use MessageTrait;
     use RequestTrait;
 
     /**