package.json: use valid SPDX string

diff --git a/package.json b/package.json
index b9d3009..8eeb043 100644 (file)
--- a/package.json
+++ b/package.json
@@ -18,7 +18,7 @@
     "c"
   ],
   "author": "Gray Leonard",
-  "license": "GNU GPL v3",
+  "license": "GPL-3.0",
   "bugs": {
     "url": "https://github.com/grayleonard/node-aubio/issues"
   },