Add strikethrough to deprecated methods in CompletionsMenu (#9086)

Adam created 

Release Notes:

- Added ([#8390](https://github.com/zed-industries/zed/issues/8390)).
- Also Grays out deprecated methods

Before

<img width="730" alt="image"
src="https://github.com/zed-industries/zed/assets/71665039/8b5e8009-22c2-43f7-b85b-79e571a5d282">

After

<img width="773" alt="image"
src="https://github.com/zed-industries/zed/assets/71665039/0aff572b-6d3f-4ed9-b08b-d925ee650817">

Change summary

crates/editor/src/editor.rs | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)

Detailed changes

crates/editor/src/editor.rs 🔗 

@@ -60,9 +60,9 @@ use gpui::{
     AnyElement, AppContext, AsyncWindowContext, BackgroundExecutor, Bounds, ClipboardItem, Context,
     DispatchPhase, ElementId, EventEmitter, FocusHandle, FocusableView, FontId, FontStyle,
     FontWeight, HighlightStyle, Hsla, InteractiveText, KeyContext, Model, MouseButton,
-    ParentElement, Pixels, Render, SharedString, Styled, StyledText, Subscription, Task, TextStyle,
-    UnderlineStyle, UniformListScrollHandle, View, ViewContext, ViewInputHandler, VisualContext,
-    WeakView, WhiteSpace, WindowContext,
+    ParentElement, Pixels, Render, SharedString, StrikethroughStyle, Styled, StyledText,
+    Subscription, Task, TextStyle, UnderlineStyle, UniformListScrollHandle, View, ViewContext,
+    ViewInputHandler, VisualContext, WeakView, WhiteSpace, WindowContext,
 };
 use highlight_matching_bracket::refresh_matching_bracket_highlights;
 use hover_popover::{hide_hover, HoverState};
@@ -930,6 +930,15 @@ impl CompletionsMenu {
                                     // Ignore font weight for syntax highlighting, as we'll use it
                                     // for fuzzy matches.
                                     highlight.font_weight = None;
+
+                                    if completion.lsp_completion.deprecated.unwrap_or(false) {
+                                        highlight.strikethrough = Some(StrikethroughStyle {
+                                            thickness: 1.0.into(),
+                                            ..Default::default()
+                                        });
+                                        highlight.color = Some(cx.theme().colors().text_muted);
+                                    }
+
                                     (range, highlight)
                                 },
                             ),