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/editor/src/git/project_diff.rs

@@ -22,10 +22,7 @@ use multi_buffer::{ExcerptId, ExcerptRange, ExpandExcerptDirection, MultiBuffer}
 use project::{Project, ProjectEntryId, ProjectPath, WorktreeId};
 use text::{OffsetRangeExt, ToPoint};
 use theme::ActiveTheme;
-use ui::{
-    div, h_flex, Color, Context, FluentBuilder, Icon, IconName, IntoElement, Label, LabelCommon,
-    ParentElement, SharedString, Styled, ViewContext, VisualContext, WindowContext,
-};
+use ui::prelude::*;
 use util::{paths::compare_paths, ResultExt};
 use workspace::{
     item::{BreadcrumbText, Item, ItemEvent, ItemHandle, TabContentParams},