revert: fix(graph): avoid repeatedly child of the same parent (#21ed76f)

- we had performance issues on benchmark `update 500->1 graph`

src/graph.luau

@@ -81,7 +81,6 @@ local function assert_stable_scope(): Node<unknown>
 end
 
 local function push_child<T>(parent: SourceNode<any>, child: Node<any>)
-    if table.find(child.parents, parent) then return end
     table.insert(parent, child)
     table.insert(child.parents, parent)
 end