Correct license and source URL of Grayscale

plugins/Grayscale.json

@@ -2,10 +2,9 @@
   "slug": "Grayscale",
   "name": "Grayscale",
   "author": "VCV",
-  "license": "BSD 3-clause",
+  "license": "proprietary",
   "version": "0.5.0",
   "manual": "https://vcvrack.com/manual/Grayscale.html",
-  "source": "https://github.com/VCVRack/Grayscale",
   "downloads": {
     "win": {
       "download": "https://vcvrack.com/downloads/plugins/Grayscale-0.5.0.zip",