Backport: chore(ai): update test message (#8875)

This is an automated backport of #8864 to the v5.0 branch.

Co-authored-by: Lars Grammel <[email protected]>

Author: vercel-ai-sdk[bot]

packages/ai/src/ui-message-stream/ui-message-chunks.test-d.ts

@@ -2,7 +2,7 @@ import { describe, expectTypeOf, it } from 'vitest';
 import { UIMessageChunk, uiMessageChunkSchema } from './ui-message-chunks';
 
 describe('UI message chunks type', () => {
-  it('should work with fixed inputSchema', () => {
+  it('parsed UI message chunk should have UIMessageChunk type', () => {
     const chunk = uiMessageChunkSchema.parse({
       type: 'text-delta',
       delta: 'Hello, world!',