Consider to give a proper value for `MultiplierUpdate`

[Dengjianping]

Recently, this pr from substrate has been merged: paritytech/substrate#12282

But they didn't set a proper value for this new type MultiplierUpdate which is Bounded::max_value().
From moonbeam side, this value is 100_000: moonbeam-foundation/moonbeam#1853

So we need to figure out what the proper value for us.