Remove derived defmt on DelayedFormat

When std i enabled, it includes std::string::String and DelayedFormat
and it fails.

Author: pebender

src/format/formatting.rs

@@ -31,7 +31,6 @@ use locales::*;
 /// This is normally constructed via `format` methods of each date and time type.
 #[cfg(feature = "alloc")]
 #[derive(Debug)]
-#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub struct DelayedFormat<I> {
     /// The date view, if any.
     date: Option<NaiveDate>,