message: docker: no need to replace crates.io source to tuna
diff: FROM rust:1.49.0
  -RUN echo '[source.crates-io] \n\
  - registry = "https://github.com/rust-lang/crates.io-index" \n\
  - replace-with = "thu" \n\
  - [source.thu] \n\
  - registry = "https://mirrors.tuna.tsinghua.edu.cn/git/crates.io-index.git"'\
  - >> /usr/local/cargo/config
  -
  RUN rustup component add clippy
  RUN rustup component add rustfmt
  