feat: remove the dependency on FusedMoE

[zhyncs]

Motivation

Modifications

Checklist

• Format your code according to the Contributor Guide.
• Add unit tests as outlined in the Contributor Guide.
• Update documentation as needed, including docstrings or example tutorials.

[zhyncs]

https://github.com/sgl-project/sglang/actions/runs/11995566939

[zhyncs]

Actually this is not a complete removal, just to avoid blocking @ispobock from continuing development on DeepSeek V2 EP.