[Update] Add Prebid Server support for Scalibur bidder

[bTimor]

🏷 Type of documentation

• update bid adapter
• new feature

📋 Checklist

• Related pull requests in prebid.js or server are linked -> New Bidder: Scalibur prebid-server#4640
• For new adapters check submitting your adapter docs

📝 Description

This PR updates the Scalibur bidder documentation to reflect the introduction of the new Prebid Server (PBS) adapter. While the client-side adapter remains active, publishers can now also utilize Scalibur through Server-to-Server (S2S) integrations.

Changes:

• Updated frontmatter metadata to set pbs: true.
• Added a new section Prebid Server Configuration (S2S) with implementation guidelines and an s2sConfig code example.
• Documented server-side video support, specifically noting the automatic VAST wrapper generation for player compatibility.
• Cleaned up document structure (heading levels and spacing) to comply with project linting rules.

The corresponding Prebid Server code implementation can be found here: prebid/prebid-server#4640

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