Auto merge of #13472 - linyihai:remove-unused-func, r=weihanglo

chore: remove the unused function

### What does this PR try to resolve?

Remove the unused function.  The code that uses this function has been removed, so it no longer makes sense to keep it.

### How should we test and review this PR?

### Additional information

src/cargo/core/resolver/context.rs

@@ -229,10 +229,3 @@ impl ResolverContext {
         graph
     }
 }
-
-impl Graph<PackageId, im_rc::HashSet<Dependency>> {
-    pub fn parents_of(&self, p: PackageId) -> impl Iterator<Item = (PackageId, bool)> + '_ {
-        self.edges(&p)
-            .map(|(grand, d)| (*grand, d.iter().any(|x| x.is_public())))
-    }
-}