update all crates msrv to 1.57 (#464)

bytestring/CHANGES.md

@@ -1,6 +1,7 @@
 # Changes
 
 ## Unreleased - 2022-xx-xx
+- Minimum supported Rust version (MSRV) is now 1.57.
 
 
 ## 1.1.0 - 2022-06-11

bytestring/src/lib.rs

@@ -72,7 +72,7 @@ impl AsRef<[u8]> for ByteString {
 
 impl AsRef<str> for ByteString {
     fn as_ref(&self) -> &str {
-        &*self
+        self
     }
 }
 
@@ -96,7 +96,7 @@ impl ops::Deref for ByteString {
 
 impl borrow::Borrow<str> for ByteString {
     fn borrow(&self) -> &str {
-        &*self
+        self
     }
 }