eplb redundant expert bugfix (#4291)

### What this PR does / why we need it?
Redundant experts bugfix
### Does this PR introduce _any_ user-facing change?
After configuring the path for experts_map, users do not need to
configure iinit_redundancy_expert.
### How was this patch tested?
The accuracy of EPLB was tested with and without the use of redundant
experts.


- vLLM version: v0.11.0
- vLLM main:
2918c1b49c

---------

Signed-off-by: shenchuxiaofugui <1311027364@qq.com>

docs/source/user_guide/feature_guide/eplb_swift_balancer.md

@@ -12,6 +12,13 @@ Expert balancing for MoE models in LLM serving is essential for optimal performa
 - Adaptive Scaling: Automatically adjusts to workload fluctuations while maintaining stable performance.
 - Fault Tolerance: Redundant expert placement ensures system resilience during hardware failures.
 
+## Support Scenarios
+
+### Models:
+DeepseekV3/V3.1/R1、Qwen3-MOE
+### MOE QuantType:
+W8A8-dynamic
+
 ## How to Use EPLB
 
 ### Dynamic EPLB