refactor: drop conc-512-tuned warmup grace override from glm5.2 b300 recipe / 移除 glm5.2 b300 recipe 中为 conc 512 调优的 warmup grace 覆盖值

AGENTIC_WARMUP_GRACE_PERIOD=3600 was tuned for the conc-512 DP8 point,
which this PR removes (DEP arm now caps at conc 64). At conc 64 the warmup
working set drains well within the default 1800s (warmup-grace-period is a
ceiling, not a fixed sleep), so fall back to the default and delete the
now-stale comment. No behavioral change at conc <= 64.

中文：AGENTIC_WARMUP_GRACE_PERIOD=3600 是为 conc 512 的 DP8 数据点调优的，而本
PR 已移除该点(DEP 分支并发上限现为 64)。在 conc 64 下，warmup 工作集会在默认
1800s 内完成 drain(warmup-grace-period 是上限而非固定等待),故回退到默认值并
删除已过时的注释。conc <= 64 下无行为变化。

Author: Oseltamivir

benchmarks/single_node/agentic/glm5.2_fp4_b300_sglang.sh

@@ -106,11 +106,6 @@ if [ "$DP_ATTENTION" = "true" ]; then
     # while KV usage sat at ~0.01). Use the cookbook's own dp8 lever from
     # the B200 cells (32768 = ~4096/rank).
     CHUNKED_PREFILL_SIZE=32768
-    # At conc 512 the saturation working set outlives the default 1800s
-    # warmup drain grace: the drain converges healthily (~0.45 req/s, zero
-    # errors) but needs ~2500s end to end. 3600 is a maximum wait, not a
-    # fixed sleep — lower-conc DPA points still finish as fast as they drain.
-    export AGENTIC_WARMUP_GRACE_PERIOD=3600
     PARALLEL_ARGS+=(
         --dp "$TP"
         --enable-dp-attention