Revert "Update guzzlehttp/guzzle requirement from 6.5.2 to 6.5.3 in /build/integration"

build/integration/composer.json

@@ -2,7 +2,7 @@
   "require-dev": {
     "phpunit/phpunit": "~6.5",
     "behat/behat": "~3.6.1",
-    "guzzlehttp/guzzle": "6.5.3",
+    "guzzlehttp/guzzle": "6.5.2",
     "jarnaiz/behat-junit-formatter": "^1.3",
     "sabre/dav": "3.2.3",
     "symfony/event-dispatcher": "~4.4"