[Core] Fix test_get_master_wheel_url

[bveeramani]

Why are these changes needed?

test_get_master_wheel_url contains the following note:

# NOTE: These should not be changed for releases.
ray_version = "3.0.0.dev0"

Because we previously changed the version for the release, the test is failing. This PR corrects the version.

Related issue number

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    method in Tune, I've added it in doc/source/tune/api/ under the
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• Testing Strategy
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