Remove built-in Unsize impls

They exist in Chalk now.

crates/ra_hir_ty/src/utils.rs

@@ -110,38 +110,6 @@ pub(super) fn all_super_trait_refs(db: &dyn HirDatabase, trait_ref: TraitRef) ->
     result
 }
 
-/// Finds a path from a trait to one of its super traits. Returns an empty
-/// vector if there is no path.
-pub(super) fn find_super_trait_path(
-    db: &dyn DefDatabase,
-    trait_: TraitId,
-    super_trait: TraitId,
-) -> Vec<TraitId> {
-    let mut result = Vec::with_capacity(2);
-    result.push(trait_);
-    return if go(db, super_trait, &mut result) { result } else { Vec::new() };
-
-    fn go(db: &dyn DefDatabase, super_trait: TraitId, path: &mut Vec<TraitId>) -> bool {
-        let trait_ = *path.last().unwrap();
-        if trait_ == super_trait {
-            return true;
-        }
-
-        for tt in direct_super_traits(db, trait_) {
-            if path.contains(&tt) {
-                continue;
-            }
-            path.push(tt);
-            if go(db, super_trait, path) {
-                return true;
-            } else {
-                path.pop();
-            }
-        }
-        false
-    }
-}
-
 pub(super) fn associated_type_by_name_including_super_traits(
     db: &dyn HirDatabase,
     trait_ref: TraitRef,