Bump Rust to 1.91.1 (#42561)

Release Notes:

- N/A

---------

Co-authored-by: Julia Ryan <juliaryan3.14@gmail.com>

crates/editor/src/editor.rs

@@ -1300,8 +1300,9 @@ struct SelectionHistoryEntry {
     add_selections_state: Option<AddSelectionsState>,
 }
 
-#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+#[derive(Copy, Clone, Default, Debug, PartialEq, Eq)]
 enum SelectionHistoryMode {
+    #[default]
     Normal,
     Undoing,
     Redoing,
@@ -1314,12 +1315,6 @@ struct HoveredCursor {
     selection_id: usize,
 }
 
-impl Default for SelectionHistoryMode {
-    fn default() -> Self {
-        Self::Normal
-    }
-}
-
 #[derive(Debug)]
 /// SelectionEffects controls the side-effects of updating the selection.
 ///