Auto merge of #10398 - piggynl:cargo-doc-fixes-1, r=weihanglo

Auto merge of #10398 - piggynl:cargo-doc-fixes-1, r=weihanglo

Fix errors in `cargo fetch` usage guide

This is a recreation of #9785.

1. By [the doc](https://doc.rust-lang.org/cargo/commands/cargo-build.html#manifest-options), `cargo build` will always access the network unless `--frozen` or `--offline` is present. Instead, `cargo fetch` will fetch dependencies, and which will allow running subsequent Cargo commands in offline mode.

2. A general template was used for `--target` that is not appropriate for `cargo fetch`.