ci: Fix installing behat dependencies

Signed-off-by: Joas Schilling <[email protected]>

Author: nickvergessen

build/integration/composer.json

@@ -2,7 +2,7 @@
   "require-dev": {
     "phpunit/phpunit": "~6.5",
     "behat/behat": "~3.10.0",
-    "guzzlehttp/guzzle": "6.5.5",
+    "guzzlehttp/guzzle": "6.5.8",
     "jarnaiz/behat-junit-formatter": "^1.3",
     "sabre/dav": "4.3.1",
     "symfony/event-dispatcher": "~4.4"