README repeats backend prerequisites and links to a removed miden-debug branch

The README currently has two identical `Backend prerequisites` sections in the debugging docs.

Both copies also link `0xMiden/miden-debug` to:

```text
https://github.com/0xMiden/miden-debug/tree/feature/vscode-dap-plugin
```

That branch now returns 404. The `miden-debug-engine` changelog in the current `miden-debug` repo shows the relevant DAP attach support has shipped, so the README should not send users to the removed feature branch anymore.

A small docs fix would remove the duplicated prerequisite block and update the `miden-debug` prerequisite wording/link to point at the released/current debugger path instead of the stale branch.

該 issue 是關於 README 檔案的。開啟儲存庫根目錄下的 README.md 檔案，找到除錯文件中的 'Backend prerequisites' 部分，並刪除重複項。將 'miden-debug' 的連結從過時的功能分支更新到主儲存庫或當前發佈路徑。透過預覽 README 來驗證變更。

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