keymap: compile Keymap::twins_in only with the ui feature, its one user

crates/keymap/src/keymap.rs

@@ -787,6 +787,7 @@ impl Keymap {
 
     /// Whether both commands of `conflict` have its chord among their defaults, so they share it by
     /// design and [`Keymap::clashing`] leaves them out.
+    #[cfg(feature = "ui")]
     pub(crate) fn twins_in(&self, conflict: &Conflict) -> bool {
         let (Some(i), Some(j)) = (self.find(&conflict.a.0), self.find(&conflict.b.0)) else { return false };
         self.twins(i, j, conflict.chord)