[Error] Documentation: Install flag `--next` does not exist.

**Describe the bug**
Instructions at https://distrobox.it/#curl-or-wget suggest a `--next` flag to the install script.

**To Reproduce**
```
$ curl -s https://raw.githubusercontent.com/89luca89/distrobox/main/install | sh -s -- --next --prefix ~/.local
Error: unknown argument --next
install --prefix /usr/local

Options:
--prefix/-P: base path where files will be deployed
(default: /usr/local if root, ~/.local otherwise)
--version/-V: release tag to install (default: 2.0.0-rc.1)
--no-color: disable color formatting
--help/-h: show this message
-v/--verbose: show more verbosity

Requires: tar plus either curl or wget. Detected architecture must be
amd64 or arm64 (matching the published release artefacts).

To uninstall, use the companion ./uninstall script.
(23) Failed writing body
```

**Expected behavior**
- Remove `--next` from the documentation.
- Add `--version` instead?

此 issue 指向 https://distrobox.it/#curl-or-wget 的文件。在 repository 中尋找安裝腳本，它可能位於根目錄或 scripts 資料夾中。透過檢查腳本的說明輸出或原始碼來確認可用的 flags。更新文件，移除 `--next` flag，並依照建議可能加入 `--version`。

由索引模型根據 Issue 內容生成。