Release v4.9.6 (#4931)

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

contracts/package.json

@@ -1,7 +1,7 @@
 {
   "name": "@openzeppelin/contracts",
   "description": "Secure Smart Contract library for Solidity",
-  "version": "4.9.5",
+  "version": "4.9.6",
   "files": [
     "**/*.sol",
     "/build/contracts/*.json",

contracts/utils/Base64.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-// OpenZeppelin Contracts (last updated v4.7.0) (utils/Base64.sol)
+// OpenZeppelin Contracts (last updated v4.9.6) (utils/Base64.sol)
 
 pragma solidity ^0.8.0;