💡 Removed main script that no longer exists

refs 481e2425af

- We no longer support using Ghost as an npm module (this was deprecated long ago)
- We've now removed the file that this used to point to (in 481e2425af)
- As we aren't supporting this approach, we are removing the main script rather than updating it

package.json

@@ -19,7 +19,6 @@
   "bugs": "https://github.com/TryGhost/Ghost/issues",
   "contributors": "https://github.com/TryGhost/Ghost/graphs/contributors",
   "license": "MIT",
-  "main": "./core/index",
   "scripts": {
     "start": "node index",
     "dev": "DEBUG=ghost:* grunt dev",