[DOC] Calcite settings documentation missing examples

[dai-chen]

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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

[AzazelSensei]

Opened #5749 — adds curl examples for the Calcite settings and fixes the v3 engine / join links.