Decrese the guzzle version restriction

Author: erussotf

composer.json

@@ -21,7 +21,7 @@
   },
   "require": {
     "php": "^7.3",
-    "guzzlehttp/guzzle": "^6.5",
+    "guzzlehttp/guzzle": "^6.0",
     "ext-json": "*",
     "ext-openssl": "*"
   },