Enable to use `DeleteDocumentsByFilter` through `IndexInterface`

[yuku]

Pull Request

Related issue

None

What does this PR do?

Add DeleteDocumentsByFilter method to IndexInterface to be able to use the method through the interface.

https://github.com/meilisearch/meilisearch-go/blob/3310833cd68e1fd42c9f63e9028edf41410e5b5c/index_documents.go#L535

Without this change, the following document doesn't work as expected.

PR checklist

Please check if your PR fulfills the following requirements:

• [x] Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
• [x] Have you read the contributing guidelines?
• [x] Have you made sure that the title is accurate and descriptive of the changes?

Thank you so much for contributing to Meilisearch!

[meili-bors[bot]]

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