suppress clippy warning

as the code is more readable this way.
Applying the recommendation IMHO, obfuscates the code for little/no benefit

src/cmd/datefmt.rs

@@ -286,6 +286,7 @@ pub fn run(argv: &[&str]) -> CliResult<()> {
  } else {
  default_tz
  };
+ #[allow(clippy::useless_let_if_seq)] // more readable this way
  let mut output_tz = if let Ok(tz) = args.flag_output_tz.parse::<Tz>() {
  tz
  } else if args.flag_output_tz.to_ascii_lowercase() == "local" {