bc5ca2c856
### What this PR does / why we need it? PR #8618 renamed `VLLM_NIXL_ABORT_REQUEST_TIMEOUT` to `VLLM_MOONCAKE_ABORT_REQUEST_TIMEOUT` and simultaneously reduced the timeout value from 300000 to 480 seconds in the nightly test configs. The 480s value is far too short for heavy multi-node workloads (DeepSeek V3/R1 under W8A8 + EP), causing [spurious abort-request timeouts](https://github.com/vllm-project/vllm-ascend/actions/runs/25067539406/job/73441223206) in CI. This PR restores the timeout value to the original 300000 to fix the nightly test failures introduced by #8618. Signed-off-by: hfadzxy <starmoon_zhang@163.com>