This referenda increases `schedulerParams.lookahead` value to 3.

## Why this change is needed?
`scheduler.lookahead` determines the size of the claim queue and at the moment is set to `2`. The claim queue shows which parachains are about to be scheduled on a specific core. A value of two shows what will be scheduled for a window of **two blocks**.

`asyncBackingParams.allowedAncestryLen` is an async backing parameter which determines the oldest relay parent a candidate can be built on. 2 here means that a candidate can be built on the latest know relay parent or the **two** relay parents before it. In total this gives a window of **three** blocks.

So we have got a discrepancy. Async backing will accept candidates based on three different blocks while the claim queue shows information only about two. Bumping `schedulerParams.lookahead` to 3 will correctly align these values.

- **Problem Statement:** Aligning `schedulerParams.lookahead` value to 3 to match the async backing parameter, resolving discrepancy in block information.
- **Significance:** Ensuring consistency in block information for scheduling parachains.
- **Proposed Solution:** Increase `schedulerParams.lookahead` value to 3.
- **Expected Outcomes:** Improved alignment between async backing and claim queue information.

#488 [Whitelisted Caller] Update schedulerParams.lookahead configuration parameter to 3