Update puffin to 0.18 (#3600)

THe profiling macros now contain unsafe code (but in a safe way), so
`#[foribd(unsafe)]` had to become `#[deny(unsafe)]`

crates/emath/src/lib.rs

@@ -20,7 +20,7 @@
 //!
 
 #![allow(clippy::float_cmp)]
-#![forbid(unsafe_code)]
+#![deny(unsafe_code)]
 
 use std::ops::{Add, Div, Mul, RangeInclusive, Sub};