remove package.json to avoid confusion

contracts/package.json

-{
-  "name": "@openzeppelin/contracts",
-  "version": "2.4.0",
-  "description": "Secure Smart Contract library for Solidity",
-  "files": [
-    "**/*.sol",
-    "/build/contracts/*.json",
-    "!/mocks",
-    "!/examples"
-  ],
-  "scripts": {
-    "prepare": "bash ../scripts/prepare-contracts-package.sh"
-  },
-  "repository": {
-    "type": "git",
-    "url": "https://github.com/OpenZeppelin/openzeppelin-contracts.git"
-  },
-  "keywords": [
-    "solidity",
-    "ethereum",
-    "smart",
-    "contracts",
-    "security",
-    "zeppelin"
-  ],
-  "author": "OpenZeppelin Community <maintainers@openzeppelin.org>",
-  "license": "MIT",
-  "bugs": {
-    "url": "https://github.com/OpenZeppelin/openzeppelin-contracts/issues"
-  },
-  "homepage": "https://github.com/OpenZeppelin/openzeppelin-contracts"
-}