Replace #[allow attributes with expect (#7796)

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

crates/epaint/src/shapes/bezier_shape.rs

@@ -1,5 +1,4 @@
-#![allow(clippy::many_single_char_names)]
-#![allow(clippy::wrong_self_convention)] // False positives
+#![expect(clippy::many_single_char_names)]
 
 use std::ops::Range;