🧹 chore: Drop redundant @testing-library/jest-dom import in FileContainer spec

`client/test/setupTests.js` already imports the matchers globally for every
Jest test in the client workspace, so the explicit import here was dead code.
Removing it brings the spec in line with the broader convention used by
`ArtifactRouting.test.tsx`, `LogContent.test.tsx`, and `attachmentTypes.test.ts`.

client/src/components/Chat/Input/Files/__tests__/FileContainer.spec.tsx

@@ -1,6 +1,5 @@
 import React from 'react';
 import { render, screen } from '@testing-library/react';
-import '@testing-library/jest-dom';
 import type { TFile } from 'librechat-data-provider';
 import FileContainer from '../FileContainer';