Issue #3282342 by xjm: Forward-port Guzzle updates, because the private testrunner doesn't like me today

Author: catch

composer.json

@@ -14,7 +14,7 @@
         "doctrine/lexer": "1.2.3",
         "doctrine/reflection": "1.2.2",
         "egulias/email-validator": "3.1.2",
-        "guzzlehttp/guzzle": "6.5.5",
+        "guzzlehttp/guzzle": "6.5.6",
         "guzzlehttp/promises": "1.5.1",
         "guzzlehttp/psr7": "1.8.5",
         "laminas/laminas-diactoros": "2.10.0",