doc: fix QuicStream direction and id nullability docs

[VivekDubey126]

Fixes: #66686

• stream.direction never returns null (it always returns 'bidi'
  or 'uni'), so the type is now {string}.
• stream.id returns null only while the stream is pending
  (lib/internal/quic/quic.js), so that case is kept and the
  "destroyed" claim is removed.
• After destruction, stream.id appears to return undefined
  because the state handle is cleared. I did not document this, to
  keep the change minimal.

[nodejs-github-bot]

Review requested:

• @nodejs/quic

[github-actions]

Welcome to Node.js, and thank you for your first contribution!

Before review, please take a moment to read:

• the guide for first-time contributors
• the contribution and automation policies
• the pull request guide
• the AI use policy
• the Code of Conduct

Please make sure every commit is signed off. For a first pull request, GitHub Actions require collaborator approval and Jenkins CI must be started by a collaborator or triager, so an initial wait is normal.

[inoway46]

This appears to be a duplicate of #66687. Could you close this PR?