LibWeb: Implement abort_a_transaction for IndexedDB

Author: https://github.com/stelar7
Commit: 2954278e37
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2696
Reviewed-by: https://github.com/gmta

Libraries/LibWeb/IndexedDB/IDBTransaction.idl

@@ -11,7 +11,7 @@ interface IDBTransaction : EventTarget {
     readonly attribute DOMException? error;
     [FIXME] IDBObjectStore objectStore(DOMString name);
     [FIXME] undefined commit();
-    [FIXME] undefined abort();
+    undefined abort();
     
     attribute EventHandler onabort;
     attribute EventHandler oncomplete;