chore(docs): update useUIStream usage

[ubmit]

I noticed that multiple docs pages were referring to the old useUIStream hook API, e.g. using isLoading instead of isStreaming. I updated all references to reflect its current API.

[vercel]

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[vercel]

The streaming documentation references a non-existent 'abort' method that was removed from the useUIStream hook API

[ubmit]

good catch, again! however, I'm not sure what should be done here. although the abort method is indeed not returned from the useUIStream hook, in this doc example the abort is being used when the "Cancel" button is clicked (as can be seen in the "Aborting Streams" section):

function App() {
  const { isLoading, generate, abort } = useUIStream({
    endpoint: '/api/generate',
  });

  return (
    <div>
      <button onClick={() => generate('Create dashboard')}>
        Generate
      </button>
      {isLoading && (
        <button onClick={abort}>Cancel</button>
      )}
    </div>
  );
}