refactor(tvix/nix-compat): address clippy in nixbase32.rs tests

Change-Id: If8820cba4cf19bf0f7aa27e0d93b70eb7b4ee81f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8221
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>

tvix/nix-compat/src/nixbase32.rs

@@ -150,7 +150,7 @@ mod tests {
             }
             None => {
                 // the decode needs to be an error
-                assert_eq!(true, super::decode(enc.as_bytes()).is_err());
+                assert!(super::decode(enc.as_bytes()).is_err());
             }
         }
     }