[release-automation] Stop adding temporary conda bin into PATH

[khluu]

The script that verifies macos wheels installs miniconda3 into a temporary directory, then exports its binary path $TMP_DIR/miniconda3/bin into PATH. This caused a problem when a new conda environment is created and activated, this path goes before the environment's bin path: https://buildkite.com/ray-project/release-automation/builds/384#018eedf8-6486-41ab-889c-2f8db37e57bd/39-286

^ In this log where I echo $PATH after activating the conda environment rayio_3.9, you can see that /Users/ec2-user/tmp.PyjQ7FlK9E/miniconda3/envs/rayio_3.9/bin is supposed to be the first in $PATH, but it's /Users/ec2-user/tmp.PyjQ7FlK9E/miniconda3/bin instead. This led the environment to use python and pip from the default miniconda installation which is on 3.8 version: https://buildkite.com/ray-project/release-automation/builds/384#018eedf8-6486-41ab-889c-2f8db37e57bd/39-268

I ran the job again without exporting and it shows that the right python and pip version from the environment was used: https://buildkite.com/ray-project/release-automation/builds/387#018eee3e-6b83-40a0-9a1b-e8164426f3e3/32-256
along with the env path being first in $PATH: https://buildkite.com/ray-project/release-automation/builds/387#018eee3e-6b83-40a0-9a1b-e8164426f3e3/32-274
The step was able to find the right distribution from ray on testpypi. It only failed because the commit was not right which is expected.

[can-anyscale]

if i remember correctly, this https://github.com/ray-project/ray/blob/master/ci/ray_ci/macos/macos_ci.sh#L93 also install miniconda; i wonder if you want to piggy back on that instead?

[khluu]

if i remember correctly, this https://github.com/ray-project/ray/blob/master/ci/ray_ci/macos/macos_ci.sh#L93 also install miniconda; i wonder if you want to piggy back on that instead?

This is installing conda in /usr/local/opt/miniconda. I think this is fine as long as the environment conda binary path can override it in $PATH like this: https://buildkite.com/ray-project/release-automation/builds/387#018eee3e-6b83-40a0-9a1b-e8164426f3e3/32-274