Update SPDX license expression.

Author: rottmann

package.json

@@ -3,10 +3,7 @@
   "version": "0.7.1",
   "description": "Core parser library to generate apidoc result following the apidoc-spec",
   "author": "Peter Rottmann <[email protected]>",
-  "license": {
-    "type": "MIT",
-    "url": "https://github.com/apidoc/apidoc-core/blob/master/LICENSE"
-  },
+  "license": "MIT",
   "main": "./lib/index.js",
   "homepage": "https://github.com/apidoc/apidoc-core",
   "repository": {