doc: mark Permission Model as completed (#1301)

Author: RafaelGSS

README.md

@@ -26,7 +26,7 @@ The program is managed through the HackerOne platform at [https://hackerone.com/
 
 | Initiative           | Champion                                         | Status                                   | Links
 |----------------------|--------------------------------------------------|------------------------------------------|-------------------------------------------------
-| Permission Model - 2 Phase | [@RafaelGSS](https://github.com/RafaelGSS) |  In Progress | [Issue #898](https://github.com/nodejs/security-wg/issues/898)
+| Permission Model - 2 Phase | [@RafaelGSS](https://github.com/RafaelGSS) |  Done | [Issue #898](https://github.com/nodejs/security-wg/issues/898)
 | Automate Security release process | [@marco-ippolito](https://github.com/marco-ippolito) | In Progress | [Issue #860](https://github.com/nodejs/security-wg/issues/860)
 | Assessment against best practices | [@fraxken](https://github.com/fraxken)/[@ulisesGascon](https://github.com/ulisesgascon) | In Progress | [Issue #859](https://github.com/nodejs/security-wg/issues/859)