Python: fix(redis): pass collection prefix as a list

[MukundaKatta]

No description provided.

[Copilot]

Pull request overview

This PR fixes Redis search index creation by passing the IndexDefinition.prefix as a list (instead of a string), matching the expected Redis client API and preventing incorrect prefix handling.

Changes:

• Update Redis connector index creation to pass prefix=[f"{collection_name}:"] to IndexDefinition.
• Update the existing unit test that creates an IndexDefinition manually to use a list prefix.
• Add a unit test asserting ensure_collection_exists() constructs IndexDefinition with a single-item prefix list for both HASH and JSON collections.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
python/semantic_kernel/connectors/redis.py	Passes collection prefix to IndexDefinition as a list during index creation.
python/tests/unit/connectors/memory/test_redis_store.py	Updates manual index-definition test and adds coverage ensuring list-prefix behavior for both collection types.

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