[core][streaming][python] Fix asyncio.wait coroutines args deprecated warnings

[rickyyx]

Why are these changes needed?

Passing coroutines directly to asyncio.wait is deprecating (warnings in >3.8, and deprecated >3.10)

We should not be doing it.

Related issue number

Closes #40250

Checks

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• I've included any doc changes needed for https://docs.ray.io/en/master/.
  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

Running the repro has no more warnings in python 3.9.

import time
import ray
import asyncio

@ray.remote(num_returns="streaming")
def task():
    for i in range(5):
        time.sleep(1)
        yield i


async def main():
    async for ref in task.remote():
        print(await ref)

asyncio.run(main())