clippy: Remove borrows that the compiler will do.

This started showing up with clippy in rust 1.64.

src/aggregation/bucket/histogram/histogram.rs

@@ -425,7 +425,7 @@ impl SegmentHistogramCollector {
         let bucket = &mut self.buckets[bucket_pos];
         bucket.doc_count += 1;
         if let Some(sub_aggregation) = self.sub_aggregations.as_mut() {
-            (&mut sub_aggregation[bucket_pos]).collect(doc, bucket_with_accessor)?;
+            sub_aggregation[bucket_pos].collect(doc, bucket_with_accessor)?;
         }
         Ok(())
     }

src/core/segment_id.rs

@@ -57,7 +57,7 @@ impl SegmentId {
     /// Picking the first 8 chars is ok to identify
     /// segments in a display message (e.g. a5c4dfcb).
     pub fn short_uuid_string(&self) -> String {
-        (&self.0.as_simple().to_string()[..8]).to_string()
+        self.0.as_simple().to_string()[..8].to_string()
     }
 
     /// Returns a segment uuid string.