chore: Mark Firecracker v1.11 unsupported

Firecracker v1.11 had reached EOL on 2025-09-18.

Signed-off-by: Takahiro Itazuri <[email protected]>

Author: zulinx86

docs/RELEASE_POLICY.md

@@ -92,7 +92,7 @@ v3.1 will be patched since were the last two Firecracker releases and less than
 | ------: | -----------: | -----------: | ------------------: | :------------------------------ |
 |   v1.13 |   2025-08-28 |      v1.13.1 |          2026-02-28 | Supported                       |
 |   v1.12 |   2025-05-07 |      v1.12.1 |          2025-11-07 | Supported                       |
-|   v1.11 |   2025-03-18 |      v1.11.0 |          2025-09-18 | Supported                       |
+|   v1.11 |   2025-03-18 |      v1.11.0 |          2025-09-18 | 2025-09-18 (end of 6mo support) |
 |   v1.10 |   2024-11-07 |      v1.10.1 |          2025-05-07 | 2025-05-07 (v1.12 released)     |
 |    v1.9 |   2024-09-02 |       v1.9.1 |          2025-03-02 | 2025-03-18 (v1.11 released)     |
 |    v1.8 |   2024-07-10 |       v1.8.0 |          2025-01-10 | 2025-01-10 (end of 6mo support) |