ci(integration): Fix avatar test with newer guzzle version

Signed-off-by: Joas Schilling <coding@schilljs.com>

Author: nickvergessen

build/integration/features/bootstrap/Avatar.php

@@ -109,7 +109,7 @@ public function loggedInUserGetsTemporaryAvatarWith(string $statusCode) {
 	 * @param string $source
 	 */
 	public function loggedInUserPostsTemporaryAvatarFromFile(string $source) {
-		$file = \GuzzleHttp\Psr7\stream_for(fopen($source, 'r'));
+		$file = \GuzzleHttp\Psr7\Utils::streamFor(fopen($source, 'r'));
 
 		$this->sendingAToWithRequesttoken('POST', '/index.php/avatar',
 			[