Use defaults for unchanged TextStyle fields (#14918)

This PR updates a number of spots where we were setting all of the
`TextStyle` fields even if we were not changing the values from the
defaults.

We now use `..Default::default()`.

Release Notes:

- N/A

crates/collab_ui/src/chat_panel/message_editor.rs

@@ -6,7 +6,7 @@ use editor::{AnchorRangeExt, CompletionProvider, Editor, EditorElement, EditorSt
 use fuzzy::{StringMatch, StringMatchCandidate};
 use gpui::{
     AsyncWindowContext, FocusableView, FontStyle, FontWeight, HighlightStyle, IntoElement, Model,
-    Render, Task, TextStyle, View, ViewContext, WeakView, WhiteSpace,
+    Render, Task, TextStyle, View, ViewContext, WeakView,
 };
 use language::{
     language_settings::SoftWrap, Anchor, Buffer, BufferSnapshot, CodeLabel, LanguageRegistry,
@@ -537,10 +537,7 @@ impl Render for MessageEditor {
             font_weight: settings.ui_font.weight,
             font_style: FontStyle::Normal,
             line_height: relative(1.3),
-            background_color: None,
-            underline: None,
-            strikethrough: None,
-            white_space: WhiteSpace::Normal,
+            ..Default::default()
         };
 
         div()

crates/collab_ui/src/collab_panel.rs

@@ -16,7 +16,7 @@ use gpui::{
     EventEmitter, FocusHandle, FocusableView, FontStyle, InteractiveElement, IntoElement,
     ListOffset, ListState, Model, MouseDownEvent, ParentElement, Pixels, Point, PromptLevel,
     Render, SharedString, Styled, Subscription, Task, TextStyle, View, ViewContext, VisualContext,
-    WeakView, WhiteSpace,
+    WeakView,
 };
 use menu::{Cancel, Confirm, SecondaryConfirm, SelectNext, SelectPrev};
 use project::{Fs, Project};
@@ -2194,10 +2194,7 @@ impl CollabPanel {
             font_weight: settings.ui_font.weight,
             font_style: FontStyle::Normal,
             line_height: relative(1.3),
-            background_color: None,
-            underline: None,
-            strikethrough: None,
-            white_space: WhiteSpace::Normal,
+            ..Default::default()
         };
 
         EditorElement::new(