[BugFix] fix mm cudagraph

[kevincheng2]

Motivation

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修复多模perfix cache 和 cudagraph 同时开启时，cuda error 700问题

cuda error 问题是由于多模调度方案修改，在高并发下会插入多条请求，导致显存使用比较极限，该问题在 #5181 已经修复

Modifications

Usage or Command

默认打开多模prefix caching 和 cudagraph

Accuracy Tests

Checklist

• Add at least a tag in the PR title.
  • Tag list: [[FDConfig],[APIServer],[Engine], [Scheduler], [PD Disaggregation], [Executor], [Graph Optimization], [Speculative Decoding], [RL], [Models], [Quantization], [Loader], [OP], [KVCache], [DataProcessor], [BugFix], [Docs], [CI], [Optimization], [Feature], [Benchmark], [Others], [XPU], [HPU], [GCU], [DCU], [Iluvatar], [Metax]]
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[paddle-bot]

Thanks for your contribution!

[Copilot]

Pull request overview

这个PR修复了多模态（multi-modal）模型同时启用prefix cache和CUDAGraph时出现的cuda error 700问题。通过移除之前强制禁用prefix caching的限制代码，允许这两个特性可以同时工作。

Key Changes

• 移除了在fastdeploy/config.py中当同时启用多模态和CUDAGraph时强制禁用prefix caching的逻辑

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
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Additional details and impacted files

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