Bump guzzlehttp/guzzle from 6.5.5 to 7.1.0

Bumps [guzzlehttp/guzzle](https://github.com/guzzle/guzzle) from 6.5.5 to 7.1.0.
- [Release notes](https://github.com/guzzle/guzzle/releases)
- [Changelog](https://github.com/guzzle/guzzle/blob/master/CHANGELOG.md)
- [Commits](guzzle/guzzle@6.5.5...7.1.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

composer.json

@@ -40,7 +40,7 @@
         "php": ">=7.0.0",
         "atoum/atoum": "^3.4",
         "firebase/php-jwt": "^5.2",
-        "guzzlehttp/guzzle": "^6.0"
+        "guzzlehttp/guzzle": "^6.0 || ^7.0"
     },
     "require-dev": {
         "friendsofphp/php-cs-fixer": "^2.16",