[ci] Add retry to rustup

[jolestar]

Rustup 会因为网络问题下载失败，需要有重试策略，避免失败。

https://github.com/rooch-network/rooch/actions/runs/9552963399/job/26330671846?pr=1913

info: checking for self-update
error: could not download file from 'https://static.rust-lang.org/rustup/release-stable.toml' to '/tmp/rustup-updatekqiRHF/release-stable.toml': failed to make network request: error sending request for url (https://static.rust-lang.org/rustup/release-stable.toml): operation timed out

有一个 Cargo 的环境变量，CARGO_NET_RETRY 不确定对 rustup 是否有效。不过这个变量也需要加上。

https://doc.rust-lang.org/cargo/reference/config.html#netretry