message: Use stable toolchain for clippy checks
  Switches the toolchain from nightly to stable to avoid unpleasant
  surprises.
diff: @@ -23,7 +23,7 @@ jobs:
  - uses: actions/checkout@v2
  - uses: actions-rs/toolchain@v1
  with:
  - toolchain: nightly
  + toolchain: stable
  components: clippy
  override: true
  - run: rustup component add clippy
  