Fix wrong clippy warning

The new lint `clippy::only_used_in_recursion` is buggy when used in traits.
rust-lang/rust-clippy#8560

serde_with/src/lib.rs

@@ -27,6 +27,10 @@
 #![doc(test(no_crate_inject))]
 #![doc(html_root_url = "https://docs.rs/serde_with/1.12.0")]
 #![cfg_attr(docsrs, feature(doc_cfg))]
+// clippy is broken and shows wrong warnings
+// clippy on stable does not know yet about the lint name
+// https://github.com/rust-lang/rust-clippy/issues/8560
+#![allow(unknown_lints, clippy::only_used_in_recursion)]
 
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