doc: mark Node.js 21.x as End-of-Life (#1018)

Author: targos

README.md

@@ -6,7 +6,6 @@
 | :--:     | :---:               | :---:        | :---:          | :---:            | :---:             | :---:                     |
 | [18.x][] | **Maintenance**     | [Hydrogen][] | 2022-04-19     | 2022-10-25       | 2023-10-18        | 2025-04-30                |
 | [20.x][] | **LTS**             | [Iron][]     | 2023-04-18     | 2023-10-24       | 2024-10-22        | 2026-04-30                |
-| [21.x][] | **Maintenance**     |              | 2023-10-17     | -                | 2024-04-01        | 2024-06-01                |
 | [22.x][] | **Current**         |              | 2024-04-24     | 2024-10-29       | 2025-10-21        | 2027-04-30                |
 | 23.x     | **Pending**         |              | 2024-10-15     | -                | 2025-04-01        | 2025-06-01                |
 | 24.x     | **Pending**         |              | 2025-04-22     | 2025-10-28       | 2026-10-20        | 2028-04-30                |
@@ -61,6 +60,7 @@ that are not End-of-Life.
 | [16.x][] | **End-of-Life** |[Gallium][]|    2021-04-20   |    2021-10-26    |       2022-10-18      | [2023-09-11][nodejs16eol] |
 | [17.x][] | **End-of-Life** |           |    2021-10-19   |         -        |                       |  2022-06-01 |
 | [19.x][] | **End-of-Life** |           |    2022-10-18   |         -        |                       |  2023-06-01 |
+| [21.x][] | **End-of-Life** |           |    2023-10-17   |         -        |       2024-04-01      |  2024-06-01 |
 
 ## Mandate