[HOT FIX] Fix bug of hybrid-ep backend in flex-dispatcher

[Autumn1998]

What does this PR do ?

Fix bug in configuration validation.
Use the official DeepEP instead of the private repository.
Related PR in dev branch: #2287

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Contribution process

flowchart LR
    A[Pre-checks] --> B[PR Tests]
    subgraph Code Review/Approval
        C1[Expert Review] --> C2[Final Review]
    end
    B --> C1
    C2 --> D[Merge]

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• I want this PR in a versioned release and have added the appropriate Milestone (e.g., Core 0.8)
• I have added relevant unit tests
• I have added relevant functional tests
• I have added proper typing to my code Typing guidelines
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[Autumn1998]

/ok to test 6094ebe

[Autumn1998]

/ok to test 6c31b39

[Autumn1998]

/ok to test 6c31b39