gpui: Don't export named Context from prelude (#21869)

This PR updates the `gpui::prelude` to not export the `Context` trait
named.

This prevents some naming clashes in downstream consumers.

Release Notes:

- N/A

crates/gpui/src/prelude.rs

@@ -3,7 +3,7 @@
 //! application to avoid having to import each trait individually.
 
 pub use crate::{
-    util::FluentBuilder, BorrowAppContext, BorrowWindow, Context, Element, FocusableElement,
+    util::FluentBuilder, BorrowAppContext, BorrowWindow, Context as _, Element, FocusableElement,
     InteractiveElement, IntoElement, ParentElement, Refineable, Render, RenderOnce,
     StatefulInteractiveElement, Styled, StyledImage, VisualContext,
 };