fix: Use the indexed metadata field 'ref_doc_id' instead of 'doc_id' during deletion.

[KutouAkira]

Description

When using llama-index-vector-stores-postgres, deleting nodes becomes extremely time-consuming when dealing with large datasets.

In line 176, an index has been added to the ref_doc_id field in the metadata during table initialization, but the doc_id field was used during deletion in line 1073 and line 1085.

Fixes # (issue)

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?

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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)

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Type of Change

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• Bug fix (non-breaking change which fixes an issue)
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[AstraBert]

Makes sense, thanks for catching it!