[BUG] Compatibility markdown needs updates

[VachaShah]

What is the bug?

The compatibility.md is out of date with client and server versions. Also needs test matrix update https://github.com/opensearch-project/opensearch-rs/blob/main/.github/workflows/test.yml#L66.

How can one reproduce the bug?

See https://github.com/opensearch-project/opensearch-rs/blob/main/COMPATIBILITY.md

What is the expected behavior?

State the compatibility between client and server versions similar to other clients. Example: https://github.com/opensearch-project/opensearch-java/blob/main/COMPATIBILITY.md

What is your host/environment?

Operating system, version.

Do you have any screenshots?

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Do you have any additional context?

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