test: Suppress needless_update for unit tests

src/write.rs

@@ -1926,6 +1926,8 @@ const EXTRA_FIELD_MAPPING: [u16; 48] = [
 ];
 
 #[cfg(test)]
+#[allow(unknown_lints)] // needless_update is new in clippy pre 1.29.0
+#[allow(needless_update)] // So we can use the same FileOptions defs with and without zopfli_buffer_size
 mod test {
     use super::{FileOptions, ZipWriter};
     use crate::compression::CompressionMethod;