ModuleNotFoundError when running on local server

On my own server (linux 18), if I create a new conda env and install flaml from scratch, the local tests (e.g., test/nlp/test_autohf.py) run into the following error:

```python
ModuleNotFoundError: No module named 'google.rpc'
2022-09-07 09:49:55,350 ERROR services.py:1489 -- Failed to start the dashboard, return code 1
The last 10 lines of /tmp/ray/session_2022-09-07_09-49-53_554284_36516/logs/dashboard.log:
File "/home/xliu127/.local/lib/python3.8/site-packages/opencensus/common/transports/sync.py", line 16, in
from opencensus.trace import execution_context
File "/home/xliu127/.local/lib/python3.8/site-packages/opencensus/trace/__init__.py", line 15, in
from opencensus.trace.span import Span
File "/home/xliu127/.local/lib/python3.8/site-packages/opencensus/trace/span.py", line 32, in
from opencensus.trace import status as status_module
File "/home/xliu127/.local/lib/python3.8/site-packages/opencensus/trace/status.py", line 15, in
from google.rpc import code_pb2
ModuleNotFoundError: No module named 'google.rpc'
```
The reason is because ray version in the current setup.py is 1.13. If instead I install ray==2.0, this problem is gone.

One potential solution is to replace ray==1.13 with ray==2.0 in setup.py