message: Specify miri toolchain for CI example
diff: @@ -146,7 +146,7 @@ nightly that *does* come with Miri:
  MIRI_NIGHTLY=nightly-$(curl -s https://rust-lang.github.io/rustup-components-history/x86_64-unknown-linux-gnu/miri)
  echo "Installing latest nightly with Miri: $MIRI_NIGHTLY"
  rustup set profile minimal
  -rustup default "$MIRI_NIGHTLY"
  +rustup override set "$MIRI_NIGHTLY"
  rustup component add miri
  cargo miri test
  