Use proper SPDX license ID in bower.json

Author: hdgarrood

bower.json

@@ -15,7 +15,7 @@
     "type": "git",
     "url": "git://github.com/slamdata/purescript-ace-halogen.git"
   },
-  "license": "Apache 2.0",
+  "license": "Apache-2.0",
   "ignore": [
     "**/.*",
     "node_modules",