Specs: move findId() to TreeScope since it wouldn't be O(1) on Element

sky/specs/apis.md

Index: sky/specs/apis.md
diff --git a/sky/specs/apis.md b/sky/specs/apis.md
index 765d674de1c9d0039a8ae101acac03d13f964b0d..afb0bede84291d27af34a821b3b63cc312b9ac2b 100644
--- a/sky/specs/apis.md
+++ b/sky/specs/apis.md
@@ -77,8 +77,6 @@ module 'sky:core' {
     void append(ChildArgument... nodes); // O(N) in number of arguments plus all their descendants
     void prepend(ChildArgument... nodes); // O(N) in number of arguments plus all their descendants
     void replaceChildrenWith(ChildArgument... nodes); // O(N) in number of descendants plus arguments plus all their descendants
-    
-    Element? findId(String id); // O(1)
   }
 
   interface Attr {
@@ -129,6 +127,8 @@ module 'sky:core' {
   abstract interface TreeScope : ParentNode {
     readonly attribute Document? ownerDocument; // O(1)
     readonly attribute TreeScope? parentScope; // O(1)
+
+    Element? findId(String id); // O(1)
   }
 
   interface ShadowRoot : TreeScope {