chore (ai): remove outdated note (vercel#6769)

Author: lgrammel

packages/ai/src/util/index.ts

@@ -1,6 +1,3 @@
-// Export stream data utilities for custom stream implementations,
-// both on the client and server side.
-// NOTE: this is experimental / internal and may change without notice
 export { cosineSimilarity } from './cosine-similarity';
 export { getTextFromDataUrl } from './data-url';
 export type { DeepPartial } from './deep-partial';