Fix warnings in preparation for Rust 1.54.0

This CL fixes several new warnings generated by rustc 1.54.0.

Bug: 194812675
Test: m rust
Change-Id: I104aaf07897db4df89dd1598969dd74221bfdd0b
diff --git a/authfs/src/fsverity/builder.rs b/authfs/src/fsverity/builder.rs
index 1842425..fda47bc 100644
--- a/authfs/src/fsverity/builder.rs
+++ b/authfs/src/fsverity/builder.rs
@@ -248,7 +248,7 @@
         let mut tree = MerkleLeaves::new();
         for (index, chunk) in test_data.chunks(CHUNK_SIZE as usize).enumerate() {
             let hash = Sha256Hasher::new()?
-                .update(&chunk)?
+                .update(chunk)?
                 .update(&vec![0u8; CHUNK_SIZE as usize - chunk.len()])?
                 .finalize()?;