chore: Fix Clippy after Rust 1.77

- There are some thread_local instances that can be made constant.
- An inner attribute can be moved to an outer one.

src/error.rs

@@ -117,9 +117,8 @@ impl error::Error for NotSupportedError {}
 impl error::Error for EventLoopError {}
 
 #[cfg(test)]
+#[allow(clippy::redundant_clone)]
 mod tests {
-    #![allow(clippy::redundant_clone)]
-
     use super::*;
 
     // Eat attributes for testing