Build: Update the license attribute

Specifying the type and URL is deprecated:

https://docs.npmjs.com/files/package.json#license
http://npm1k.org/

(cherry-picked from 8e92e1ea3c533f3be82c99bbafaaf74b5bdedecc)

Fixes gh-2331
Closes gh-2330

package.json

@@ -22,12 +22,7 @@
   "bugs": {
     "url": "https://github.com/jquery/jquery/issues"
   },
-  "licenses": [
-    {
-      "type": "MIT",
-      "url": "https://github.com/jquery/jquery/blob/compat/LICENSE.txt"
-    }
-  ],
+  "license": "MIT",
   "dependencies": {},
   "devDependencies": {
     "commitplease": "2.0.0",