fix(lint): Replace delete operator with undefined assignment

Biome's noDelete lint rule flags the delete operator for performance.
Since changelog is an optional field and JSON.stringify omits undefined
values, the behavior is identical.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: ericapisani

scripts/clear_attribute_changelog.ts

@@ -15,7 +15,7 @@ async function clearAll(): Promise<void> {
     const json: AttributeJson = JSON.parse(content);
 
     if ('changelog' in json) {
-      delete json.changelog;
+      json.changelog = undefined;
       await fs.promises.writeFile(filePath, `${JSON.stringify(json, null, 2)}\n`, 'utf-8');
       count++;
     }
@@ -34,7 +34,7 @@ async function clearByKey(key: string): Promise<void> {
 
     if (json.key === key) {
       if ('changelog' in json) {
-        delete json.changelog;
+        json.changelog = undefined;
         await fs.promises.writeFile(filePath, `${JSON.stringify(json, null, 2)}\n`, 'utf-8');
         console.log(`Cleared changelog from ${relativeFile}`);
       } else {