refactor(tvix/serde): cargo clippy

Change-Id: I3c86225040a04c9cb5702b226b4a5008ae219c42
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9093
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI

tvix/serde/src/error.rs

@@ -64,7 +64,7 @@ impl Display for Error {
                 )?;
 
                 for err in errors {
-                    writeln!(f, "{}", err.fancy_format_str(&source))?;
+                    writeln!(f, "{}", err.fancy_format_str(source))?;
                 }
 
                 Ok(())