epochLength is not set on synchronizer.settings

[vimwitch]

Describe the bug
The epochLength value is not set during setup here.

[vivianjeng]

It should be in attester settings

Unirep/packages/core/src/Synchronizer.ts

Lines 297 to 300 in 67b2b59

	this._attesterSettings[toDecString(attesterId)] = {
	startTimestamp: Number(timestamp),
	epochLength: Number(epochLength),
	}

Since it might sync many attesters
but we can remove the epochLength in settings