Remove nyholm/psr7 from require-dev (#928)

* Remove nyholm/psr7 from require-dev

* cs

Author: Nyholm

composer.json

@@ -20,8 +20,7 @@
         "phpunit/phpunit": "6.3.*",
         "geocoder-php/provider-integration-tests": "^1.0",
         "php-http/message": "^1.0",
-        "php-http/curl-client": "^1.7",
-        "nyholm/psr7": "^0.2.2"
+        "php-http/curl-client": "^1.7"
     },
     "provide": {
         "geocoder-php/provider-implementation": "1.0"