message: Replace remaining uses of `[project]` in documentation with `[package]`
  The `[project]` section is not currently referenced anywhere else in the documentation, so the use here confused me. It seems to be a deprecated alias for `[package]`, which is documented, so let's swap it.
diff: @@ -115,7 +115,7 @@ appropriate `cargo-features`:
  ```toml
  cargo-features = ["publish-lockfile"]
  -[project]
  +[package]
  ...
  publish-lockfile = true
  ```
  @@ -263,7 +263,7 @@ for features and dependencies are separated. The effect of this is that, in the
  feature requirements, dependencies have to be prefixed with `crate:`. Like this:
  ```toml
  -[project]
  +[package]
  namespaced-features = true
  [features]
  