Remove codesniffer from composer.json.

Author: Nyholm

composer.json

@@ -17,8 +17,7 @@
         "php-http/client-implementation": "^1.0",
         "php-http/httplug": "^1.0",
         "php-http/discovery": "^1.0",
-        "paragonie/random_compat": "^2.0",
-        "squizlabs/php_codesniffer": "^2.7"
+        "paragonie/random_compat": "^2.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^4.8 || ^5.6",