fix copy paste error about low-level example description (#730)

the custom_tree_owned_partial description was the same as the unsafe example.

src/lib.rs

@@ -54,7 +54,7 @@
 //! Examples which show usage of the low-level API are:
 //!
 //!   - [custom_tree_vec](https://github.com/DioxusLabs/taffy/blob/main/examples/custom_tree_vec.rs) which implements a custom Taffy tree using a `Vec` as an arena with NodeId's being index's into the Vec.
-//!   - [custom_tree_owned_partial](https://github.com/DioxusLabs/taffy/blob/main/examples/custom_tree_owned_partial.rs) which implements a custom Taffy tree using directly owned children with NodeId's being pointers.
+//!   - [custom_tree_owned_partial](https://github.com/DioxusLabs/taffy/blob/main/examples/custom_tree_owned_partial.rs) which implements a custom Taffy tree using directly owned children with NodeId's being index's into vec on parent node.
 //!   - [custom_tree_owned_unsafe](https://github.com/DioxusLabs/taffy/blob/main/examples/custom_tree_owned_unsafe.rs) which implements a custom Taffy tree using directly owned children with NodeId's being pointers.
 
 // document the feature flags for the crate by extracting the comments from Cargo.toml