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.rs

@@ -1,6 +1,6 @@
-// todo!(linux): remove
+// todo(linux): remove
 #![cfg_attr(target_os = "linux", allow(dead_code))]
-// todo!("windows"): remove
+// todo("windows"): remove
 #![cfg_attr(windows, allow(dead_code))]
 
 mod app_menu;
@@ -63,7 +63,7 @@ pub(crate) fn current_platform() -> Rc<dyn Platform> {
 pub(crate) fn current_platform() -> Rc<dyn Platform> {
     Rc::new(LinuxPlatform::new())
 }
-// todo!("windows")
+// todo("windows")
 #[cfg(target_os = "windows")]
 pub(crate) fn current_platform() -> Rc<dyn Platform> {
     unimplemented!()