Replace #[allow attributes with expect (#7796)

We do have `clippy::allow_attributes` turned on, but it doesn't seem to
work properly

crates/eframe/src/stopwatch.rs

@@ -1,4 +1,4 @@
-#![allow(dead_code)] // not everything is used on wasm
+#![allow(clippy::allow_attributes, dead_code)] // not used on all platforms
 
 use web_time::Instant;