Correcting Redis URL/Client handling

[AstraBert]

Description

In llama-index-vector-store-redis v0.5.1 we incorrectly check for the redis_client, so that the RedisVectorStore object cannot be loaded simply from a URL anymore. With this PR, we correct the redis client handling so that the client is instatiated from the URL, if the redis_client itself is not passed.

Fixes #18981

New Package?

Did I fill in the tool.llamahub section in the pyproject.toml and provide a detailed README.md for my new integration or package?

• Yes
• No

Version Bump?

Did I bump the version in the pyproject.toml file of the package I am updating? (Except for the llama-index-core package)

• Yes
• No

Type of Change

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

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• I believe this change is already covered by existing unit tests

Suggested Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added Google Colab support for the newly added notebooks.
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I ran uv run make format; uv run make lint to appease the lint gods

[logan-markewich]

We can use Redis.from_url() I think? Slightly safer

[AstraBert]

Yup :)