Relax notWhileSyncing

### Describe the bug

when `clockSlot - headSlot > 32`, we throw error and not allow validators to query/execute their duties
this is too strict, because post-fulu we may not have 32 blocks but we could have proposer duties ahead

https://discord.com/channels/593655374469660673/1530112297391886427/1541995551296585758

### Expected behavior

If there are proposer duties ahead in the head state, we should let validators get/execute their duties

### Steps to reproduce

_No response_

### Additional context

_No response_

### Operating system

Linux

### Lodestar version or commit hash

unstable

No file or test is identified in the issue. Start by locating the notWhileSyncing check that compares clockSlot and headSlot, then trace how proposer duties are represented in the head state. Done means validators can query or execute duties when proposer duties are ahead despite clockSlot - headSlot exceeding 32, with regression coverage for the relaxed behavior.

Written by the indexing model from the issue text.