message: Remove `rustup toolchain update stable` from CI, it is no longer necessary.
  GitHub Actions' environments now contain a sufficiently-new stable toolchain for `libtock-rs`. Remove the toolchain update step, as it is now a waste of time.
diff: @@ -40,15 +40,9 @@ jobs:
  # using the RUSTFLAGS environment variable because if we set RUSTFLAGS
  # cargo will ignore the rustflags config in .cargo/config, breaking
  # relocation.
  - #
  - # TODO: Remove the "rustup toolchain update stable" once the 20220227.1
  - # version of the Ubuntu 20.04 virtual environment is fully rolled out.
  - # The rollout status can be found here:
  - # https://github.com/actions/virtual-environments
  - name: Build and Test
  run: |
  sudo apt-get install ninja-build
  - rustup toolchain update stable
  cd "${GITHUB_WORKSPACE}"
  echo "[target.'cfg(all())']" >> .cargo/config
  echo 'rustflags = ["-D", "warnings"]' >> .cargo/config
  