gpui: Don't impl IntoElement on () (#8555)

Although it's kinda cute, rust makes it too easy to accidentally return
() from a function.

/cc @nathansobo

Release Notes:

- N/A

crates/gpui/src/interactive.rs

@@ -1,5 +1,6 @@
 use crate::{
-    point, seal::Sealed, IntoElement, Keystroke, Modifiers, Pixels, Point, Render, ViewContext,
+    point, seal::Sealed, Empty, IntoElement, Keystroke, Modifiers, Pixels, Point, Render,
+    ViewContext,
 };
 use smallvec::SmallVec;
 use std::{any::Any, fmt::Debug, ops::Deref, path::PathBuf};
@@ -343,7 +344,8 @@ impl ExternalPaths {
 
 impl Render for ExternalPaths {
     fn render(&mut self, _: &mut ViewContext<Self>) -> impl IntoElement {
-        // Intentionally left empty because the platform will render icons for the dragged files
+        // the platform will render icons for the dragged files
+        Empty
     }
 }