Remove v5.0 release candidate note and add audit (#4663)

Co-authored-by: Francisco Giordano <[email protected]>
(cherry picked from commit a754936)

Author: ernestognw

README.md

@@ -1,7 +1,3 @@
-> [!NOTE]
-> Version 5.0 is currently in release candidate period. Bug bounty rewards are boosted 50% until the release.  
-> [See more details on Immunefi.](https://immunefi.com/bounty/openzeppelin/)
-
 # <img src="logo.svg" alt="OpenZeppelin" height="40px">
 
 [![NPM Package](https://img.shields.io/npm/v/@openzeppelin/contracts.svg)](https://www.npmjs.org/package/@openzeppelin/contracts)

audits/2023-10-v5.0.pdf

@@ -2,6 +2,7 @@
 
 | Date         | Version | Commit    | Auditor      | Scope                | Links                                                       |
 | ------------ | ------- | --------- | ------------ | -------------------- | ----------------------------------------------------------- |
+| October 2023 | v5.0.0  | `b5a3e69` | OpenZeppelin | v5.0 Changes         | [🔗](./2023-10-v5.0.pdf)                                    |
 | May 2023     | v4.9.0  | `91df66c` | OpenZeppelin | v4.9 Changes         | [🔗](./2023-05-v4.9.pdf)                                    |
 | October 2022 | v4.8.0  | `14f98db` | OpenZeppelin | ERC4626, Checkpoints | [🔗](./2022-10-ERC4626.pdf) [🔗](./2022-10-Checkpoints.pdf) |
 | October 2018 | v2.0.0  | `dac5bcc` | LevelK       | Everything           | [🔗](./2018-10.pdf)                                         |