Update license in composer.json.

composer.json

@@ -7,11 +7,11 @@
     "php": ">=5.2",
     "composer/installers": "^1.0"
   },
-  "license": "GPLv2 or later",
+  "license": "GPL-2.0-or-later",
   "authors": [
     {
       "name": "John James Jacoby",
       "email": "johnjamesjacoby@me.com"
     }
   ]
-}
\ No newline at end of file
+}