add some info to composer

composer.json

 {
     "name": "netinventors/next-tool-kit",
-    "description": "",
+    "description": "Provides some handy tools for shopware 6",
     "version": "4.0.0",
     "type": "shopware-platform-plugin",
     "license": "proprietary",
@@ -16,7 +16,6 @@
     "minimum-stability": "RC",
     "extra": {
         "shopware-plugin-class": "NetInventors\\NetiNextToolKit\\NetiNextToolKit",
-        "plugin-icon": "src/Resources/plugin.png",
         "label": {
             "de-DE": "ToolKit",
             "en-GB": "ToolKit"