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the newly outdated states.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.

[alysiahuggins]

This will not be addressed right now however we have created an issue to set a max state history retention period allowed #2114