[chore] Use local import for conda instead (#51290)

`conda` is not specified in `requirements.txt`. A ModuleNotFoundError is
thrown when I try to run a test in the file for debugging.

Signed-off-by: Kai-Hsun Chen <kaihsun@anyscale.com>

Author: kevin85421

python/ray/tests/test_task_events.py

@@ -1,7 +1,6 @@
 from collections import defaultdict
 from typing import Dict
 
-import conda
 import os
 import pytest
 import sys
@@ -272,6 +271,8 @@ def task():
 
 
 def test_failed_task_runtime_env_setup(shutdown_only):
+    import conda
+
     @ray.remote
     def f():
         pass