[CHORE] cleanup Debug of HnswIndexProvider (#2864)

## Description of changes

*Summarize the changes made by this PR.*
 - Small refactor.

## Test plan
*How are these changes tested?*

- [ ]  `cargo check` locally; ci remotely

## Documentation Changes
*Are all docstrings for user-facing APIs updated if required? Do we need
to make documentation changes in the [docs
repository](https://github.com/chroma-core/docs)?*

No

rust/index/src/hnsw_provider.rs

@@ -71,11 +71,9 @@ impl Cacheable for HnswIndexRef {
 
 impl Debug for HnswIndexProvider {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(
-            f,
-            "HnswIndexProvider {{ temporary_storage_path: {:?} }}",
-            self.temporary_storage_path,
-        )
+        f.debug_struct("HnswIndexProvider")
+            .field("temporary_storage_path", &self.temporary_storage_path)
+            .finish_non_exhaustive()
     }
 }