Rate-limit commission *increases* only

[cwgoes]

Ref https://github.com/cosmos/cosmos-sdk/blob/develop/x/staking/types/commission.go#L122

There's no reason we need to rate-limit commission rate decreases (that I can think of).

This is quite annoying.

cc @rigelrozanski Can you think of any reason to rate-limit decreases I'm missing?

[rigelrozanski]

You're correct, if you're decreasing your commission there is no good reason to rate limit - we ought to remove that .Abs()

[alexanderbez]

This was done by me as it was the definition of commission rate change I had at the time of implementation -- i.e. any change should be rate limited. I see this is not desirable obviously so I'll go ahead and fix this asap.