shared: remove pointless as_ref

I believe the signature of the constructor was originally generic over
`AsRef<[u8]>`, but it got changed to be concrete. However, the
implementation continued calling `as_ref()` unnecessarily. This looks
harmless, but exposes us to inference failures.

Ref rust-lang/rust#139441

Author: BurntSushi

src/shared/posix.rs

@@ -22,8 +22,7 @@ impl PosixTimeZone<Abbreviation> {
         // `0..=24`.) Requiring strict POSIX rules doesn't seem necessary
         // since the extension is a strict superset. Plus, GNU tooling
         // seems to accept the extension.
-        let parser =
-            Parser { ianav3plus: true, ..Parser::new(bytes.as_ref()) };
+        let parser = Parser { ianav3plus: true, ..Parser::new(bytes) };
         parser.parse()
     }
 
@@ -34,8 +33,7 @@ impl PosixTimeZone<Abbreviation> {
     pub fn parse_prefix<'b>(
         bytes: &'b [u8],
     ) -> Result<(PosixTimeZone<Abbreviation>, &'b [u8]), Error> {
-        let parser =
-            Parser { ianav3plus: true, ..Parser::new(bytes.as_ref()) };
+        let parser = Parser { ianav3plus: true, ..Parser::new(bytes) };
         parser.parse_prefix()
     }
     // only-jiff-end