fix: allow gho steward param change in both directions

[brotherlymite]

For more flexibility and feedback from riskCouncil, I think the GhoStewardV2 should allow changing the facilitatorBucketCapacity, ghoBorrowCap, gsmExposureCap, gsmBuySellFees in both the directions (increase / decrease).

Should be quite straightforward using the _isDifferenceLowerThanMax method instead of _isIncreaseLowerThanMax.

Also this comment, should be patched from PoolAdmin to RiskAdmin imo and the tests should be fixed as the RiskAdmin role should be sufficient.

[miguelmtzinf]

Thanks @brotherlymite for raising this issue.

Steward design and capabilities are decided by governance discussion. #402 updates the contract based on the last discussion of the gov thread.
The design and capabilities of the steward are determined through governance discussions. PR#402 modifies the contract in line with the latest discussions from the governance thread.

#402 fixes the nastpec docs of the contract, so closing this issue now.