build(deps-dev): bump guzzlehttp/psr7 from 1.6.1 to 1.7.0

Bumps [guzzlehttp/psr7](https://github.com/guzzle/psr7) from 1.6.1 to 1.7.0.
- [Release notes](https://github.com/guzzle/psr7/releases)
- [Changelog](https://github.com/guzzle/psr7/blob/1.7.0/CHANGELOG.md)
- [Commits](guzzle/psr7@1.6.1...1.7.0)

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

Author: dependabot[bot]

composer.json

@@ -21,7 +21,7 @@
     },
     "require-dev": {
         "friendsofphp/php-cs-fixer": "^2.16",
-        "guzzlehttp/psr7": "^1.5",
+        "guzzlehttp/psr7": "^1.7",
         "http-interop/http-factory-guzzle": "^1.0",
         "infection/infection": "^0.11.5",
         "php-http/mock-client": "^1.1",