Fix license

Author: Jord-JD

composer.json

@@ -4,7 +4,7 @@
     "description": "This library handles various UK postcode related tasks such as address lookup by postcode, postcode validation, generation of valid UK postcodes and getting a postcode's outward and inward codes.",
     "keywords": ["postcodes", "PHP", "PHP library", "PHP postcodes library", "PHP postcodes"],
     "homepage": "https://github.com/rapidwebltd/php-postcodes",
-    "license": "LGPL3",
+    "license": "LGPL-3.0-only",
     "require": {
         "php": ">=5.5.9",
         "guzzlehttp/guzzle": "~6.0",