chore(docs): update release calendar for 2.21 patches (coder#17605)

Author: stirby

docs/install/releases/index.md

@@ -60,9 +60,9 @@ pages.
 | [2.16](https://coder.com/changelog/coder-2-16) | October 01, 2024  | Not Supported    | [v2.16.1](https://github.com/coder/coder/releases/tag/v2.16.1) |
 | [2.17](https://coder.com/changelog/coder-2-17) | November 05, 2024 | Not Supported    | [v2.17.3](https://github.com/coder/coder/releases/tag/v2.17.3) |
 | [2.18](https://coder.com/changelog/coder-2-18) | December 03, 2024 | Not Supported    | [v2.18.5](https://github.com/coder/coder/releases/tag/v2.18.5) |
-| [2.19](https://coder.com/changelog/coder-2-19) | February 04, 2025 | Security Support | [v2.19.1](https://github.com/coder/coder/releases/tag/v2.19.1) |
-| [2.20](https://coder.com/changelog/coder-2-20) | March 04, 2025    | Stable           | [v2.20.2](https://github.com/coder/coder/releases/tag/v2.20.2) |
-| [2.21](https://coder.com/changelog/coder-2-21) | April 01, 2025    | Mainline         | [v2.21.0](https://github.com/coder/coder/releases/tag/v2.21.0) |
+| [2.19](https://coder.com/changelog/coder-2-19) | February 04, 2025 | Security Support | [v2.19.3](https://github.com/coder/coder/releases/tag/v2.19.3) |
+| [2.20](https://coder.com/changelog/coder-2-20) | March 04, 2025    | Stable           | [v2.20.3](https://github.com/coder/coder/releases/tag/v2.20.3) |
+| [2.21](https://coder.com/changelog/coder-2-21) | April 01, 2025    | Mainline         | [v2.21.3](https://github.com/coder/coder/releases/tag/v2.21.3) |
 | 2.22                                           | May 06, 2025      | Not Released     | N/A                                                            |
 <!-- RELEASE_CALENDAR_END -->