Remove ! from todo!() in comments (#8643)

This practice makes it difficult to locate todo!s in my code when I'm
working. Let's take out the bang if we want to keep doing this.

Release Notes:

- N/A

crates/gpui/src/platform/linux/wayland.rs

@@ -1,4 +1,4 @@
-//todo!(linux): remove this once the relevant functionality has been implemented
+// todo(linux): remove this once the relevant functionality has been implemented
 #![allow(unused_variables)]
 
 pub(crate) use client::*;