chore: Bump Rust version to 1.80 (#15186)

Release Notes:

- N/A

crates/markdown/src/markdown.rs

@@ -216,7 +216,7 @@ impl Selection {
     }
 }
 
-#[derive(Clone)]
+#[derive(Clone, Default)]
 pub struct ParsedMarkdown {
     source: SharedString,
     events: Arc<[(Range<usize>, MarkdownEvent)]>,
@@ -232,15 +232,6 @@ impl ParsedMarkdown {
     }
 }
 
-impl Default for ParsedMarkdown {
-    fn default() -> Self {
-        Self {
-            source: SharedString::default(),
-            events: Arc::from([]),
-        }
-    }
-}
-
 pub struct MarkdownElement {
     markdown: View<Markdown>,
     style: MarkdownStyle,