Merge #659

659: Fix clippy error to add clippy job on Ci r=Kerollmops a=unvalley

## Related PR
This PR is for #673 

## What does this PR do?
- ~~add `Run Clippy` job to CI (rust.yml)~~
- apply `cargo clippy --fix` command
- fix some `cargo clippy` error manually (but warnings still remain on tests)

## PR checklist
Please check if your PR fulfills the following requirements:
- [x] Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
- [x] Have you read the contributing guidelines?
- [x] Have you made sure that the title is accurate and descriptive of the changes?


Co-authored-by: unvalley <kirohi.code@gmail.com>
Co-authored-by: unvalley <38400669+unvalley@users.noreply.github.com>

milli/src/heed_codec/facet/mod.rs

@@ -88,8 +88,7 @@ impl<'a> heed::BytesEncode<'a> for FacetGroupValueCodec {
     type EItem = FacetGroupValue;
 
     fn bytes_encode(value: &'a Self::EItem) -> Option<Cow<'a, [u8]>> {
-        let mut v = vec![];
-        v.push(value.size);
+        let mut v = vec![value.size];
         CboRoaringBitmapCodec::serialize_into(&value.bitmap, &mut v);
         Some(Cow::Owned(v))
     }