Bump @openzeppelin/contracts from 3.1.0 to 4.9.6

Bumps [@openzeppelin/contracts](https://github.com/OpenZeppelin/openzeppelin-contracts) from 3.1.0 to 4.9.6.
- [Release notes](https://github.com/OpenZeppelin/openzeppelin-contracts/releases)
- [Changelog](https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/CHANGELOG.md)
- [Commits](OpenZeppelin/openzeppelin-contracts@v3.1.0...v4.9.6)

---
updated-dependencies:
- dependency-name: "@openzeppelin/contracts"
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>

package.json

@@ -23,7 +23,7 @@
   "devDependencies": {
     "@nomiclabs/hardhat-ethers": "^2.0.6",
     "@nomiclabs/hardhat-waffle": "^2.0.3",
-    "@openzeppelin/contracts": "3.1.0",
+    "@openzeppelin/contracts": "4.9.6",
     "@types/chai": "^4.2.6",
     "@types/mocha": "^5.2.7",
     "axios": "^0.20.0",

yarn.lock

@@ -735,10 +735,10 @@
   resolved "https://registry.yarnpkg.com/@nomiclabs/hardhat-waffle/-/hardhat-waffle-2.0.6.tgz#d11cb063a5f61a77806053e54009c40ddee49a54"
   integrity sha512-+Wz0hwmJGSI17B+BhU/qFRZ1l6/xMW82QGXE/Gi+WTmwgJrQefuBs1lIf7hzQ1hLk6hpkvb/zwcNkpVKRYTQYg==
 
-"@openzeppelin/contracts@3.1.0":
-  version "3.1.0"
-  resolved "https://registry.yarnpkg.com/@openzeppelin/contracts/-/contracts-3.1.0.tgz#bcea457ef89069fbe5a617f50b25b6a8272895d5"
-  integrity sha512-dVXDnUKxrAKLzPdCRkz+N8qsVkK1XxJ6kk3zuI6zaQmcKxN7CkizoDP7lXxcs/Mi2I0mxceTRjJBqlzFffLJrQ==
+"@openzeppelin/contracts@4.9.6":
+  version "4.9.6"
+  resolved "https://registry.yarnpkg.com/@openzeppelin/contracts/-/contracts-4.9.6.tgz#2a880a24eb19b4f8b25adc2a5095f2aa27f39677"
+  integrity sha512-xSmezSupL+y9VkHZJGDoCBpmnB2ogM13ccaYDWqJTfS3dbuHkgjuwDFUmaFauBCboQMGB/S5UqUl2y54X99BmA==
 
 "@resolver-engine/core@^0.3.3":
   version "0.3.3"