Fix tutorials/qaoa.ipynb as part of docs cleanup for Cirq 1.0 (quantumlib#5200)

* Change example device from `cg.Bristlecone` (now deprecated) to `cg.Sycamore`.
* Use new GridDeviceMetadata instead of deprecated device properties (like neighbors_of)
* Move import to top
* Clear outputs

Author: tanujkhattar