fix: remove ws publishing from synced flashblocks

[noot]

📝 Summary

removal of logic in #310

💡 Motivation and Context

we don't want non-active builders to publish flashblocks to ws, as it requires additional rollup-boost changes.

✅ I have completed the following steps:

• Run make lint
• Run make test
• Added tests (if applicable)

[Copilot]

Pull Request Overview

This PR removes WebSocket publishing functionality from the synced flashblocks code path. The change eliminates the ws_pub parameter and its associated publishing logic when handling synced flashblocks, while keeping the execution and payload event handling intact.

Key Changes:

• Removed WebSocketPublisher dependency and parameter passing through the payload handler
• Eliminated WebSocket publishing code block and related metrics recording for synced flashblocks
• Cleaned up unused metrics() accessor method

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
crates/op-rbuilder/src/builders/flashblocks/service.rs	Removed ws_pub parameter from PayloadHandler initialization
crates/op-rbuilder/src/builders/flashblocks/payload_handler.rs	Removed WebSocketPublisher import, struct field, constructor parameter, and publishing logic from payload execution handler
crates/op-rbuilder/src/builders/flashblocks/ctx.rs	Removed unused metrics() accessor method

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