[Tests] move qwen3 performance test from nightly to e2e (#5980)

### What this PR does / why we need it?
Move the qwen3 performance test from nightly to e2e to intercept
performance degradation.

- vLLM version: v0.13.0
- vLLM main:
2c24bc6996

---------

Signed-off-by: wxsIcey <1790571317@qq.com>

tests/e2e/multicard/2-cards/test_qwen3_performance.py

@@ -37,14 +37,14 @@ api_keyword_args = {
 
 vllm_bench_cases = {
     "dataset-name": "random",
-    "num_prompts": 1000,
+    "num_prompts": 500,
     "request_rate": 20,
     "random_input_len": 128,
     "max_concurrency": 40,
     "random_output_len": 100,
 }
 
-baseline_throughput = 1622.08  # baseline throughput for Qwen3-8B
+baseline_throughput = 1600.0  # baseline throughput for Qwen3-8B, measured with num_prompts=500
 
 
 @pytest.mark.parametrize("model", MODELS)