Add description of how automatical idling works with RMV and S3 Queue

[Blargian]

Adds comment regarding automatic idling behaviour with refreshable materialised views and S3 queue. Closes #3041

Checklist

• Delete items not relevant to your PR
• URL changes should add a redirect to the old URL via https://github.com/ClickHouse/clickhouse-docs/blob/main/docusaurus.config.js
• If adding a new integration page, also add an entry to the integrations list here: https://github.com/ClickHouse/clickhouse-docs/blob/main/docs/en/integrations/index.mdx