[CI] Remove benchmark patch and increase the scheduler frequency (#1762)

### What this PR does / why we need it?
This pr purpose to do the following things:
1. Remove `benchmark_datasets.py` patch
2. Increase the scheduler frequency to 2 times per day, due to the
recent large number of daily submissions, we need to increase the
default test time(6h)
### Does this PR introduce _any_ user-facing change?

### How was this patch tested?


- vLLM version: v0.9.2
- vLLM main:
247102f07f

---------

Signed-off-by: wangli <wangli858794774@gmail.com>

.github/workflows/nightly_benchmarks.yaml

@@ -20,9 +20,10 @@ name: 'Benchmarks / Performance'
 
 on:
   schedule:
-    # Run at 02:00 everyday
-    - cron: '00 18 * * *'
-  
+    # Run benchmarks at 20:00 and 03:00 Beijing time (UTC+8)
+    - cron: "0 12 * * *"
+    - cron: "0 19 * * *"
+
   workflow_dispatch:
     # Allow manual triggering of the workflow