Update composer.json, fixing license for packagist

composer.json

@@ -3,7 +3,7 @@
   "type": "typo3-cms-extension",
   "description": "Contains some useful tools like a testing tool for redirects, a link checker, a back link checker and a content comparison tool between the same or different urls. Furthermore there is full scheduler support for all tests and synchronization tasks.",
   "homepage": "https://www.sgalinski.de",
-  "license": ["GPL-2.0+"],
+  "license": ["GPL-2.0-or-later"],
   "version": "2.0.7",
   "support": {
     "issues": "https://gitlab.sgalinski.de/typo3/df_tools/issues"