CCM-12327: typecheck fix post merge

Author: harrim91

frontend/src/__tests__/components/organisms/PreviewLetterTemplate.test.tsx

@@ -165,6 +165,7 @@ describe('PreviewLetterTemplate component', () => {
           proofingEnabled: true,
           createdAt: '2025-04-02T09:33:25.729Z',
           updatedAt: '2025-04-02T09:33:25.729Z',
+          lockNumber: 1,
         }}
       />
     );