I05: Inability to reduce stateHistoryRetentionPeriod

[alysiahuggins]

Affected Code: LightClient.sol (line 441)

Summary: The function setstateHistoryRetentionPeriod wrongly when reducing the retention period, which can lock in a large value if set by mistake.

Suggestion: Instead of reverting when the retention period decreases, updateStateHistory could be called with the last finalized state to delete the newly outdated states.

Comments: This was intentional for this version of the escape hatch but will address later.