[DEVREL-144] remove beta language and promote to GA

[jazzsequence]

Removes beta language from the Elasticsearch documentation following the GA launch.

Changes

• Remove <Partial file="elasticsarch-pre-ga.md" /> include from all four guide pages
• Rewrite the Support section in the introduction to use standard Dashboard support language (removes beta Slack channel reference)
• Update the "Do I have to pay extra?" FAQ to remove beta phase language
• Remove the Status row from the search comparison table (both products are now GA)
• Embed the Elasticsearch demo video on the introduction page
• Bump reviewed date to 2026-06-16 on all modified pages

[pantheon-site-integration]

Successfully created multidev environment: pr-10120