feat: remove useless code change

Signed-off-by: SuZhou-Joe <suzhou@amazon.com>

src/core/types/saved_objects.ts

@@ -115,7 +115,7 @@ export interface SavedObject<T = unknown> {
    */
   originId?: string;
   /** Workspaces that this saved object exists in. */
-  workspaces?: string[] | null;
+  workspaces?: string[];
   /** Permissions that this saved objects exists in. */
   permissions?: Permissions;
 }