[DOC] Calcite settings documentation missing examples

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The Calcite settings documentation is missing concrete examples and contains a broken reference:

1. The Calcite settings section does not include example showing how users can actually modify these settings.
2. The reference to introduce v3 engine appears to be broken.

Reference: https://github.com/opensearch-project/sql/blob/main/docs/user/admin/settings.rst#plugins-calcite-enabled

Version: 2.19 - 3.3

What other resources are available? N/A

Start in docs/user/admin/settings.rst at the Calcite settings section, especially the plugins-calcite-enabled reference and the broken introduce v3 engine link. Check nearby documentation for the supported way to modify settings, then add concrete examples and repair the reference; the issue is done when both requests are reflected in the documentation.