feat(nns): Change the minimum maturity disbursement from 1/0.95 to 1

[jasonz-dfinity]

Why

When maturity disbursement feature was added, it used the same minimum for the spawning neurons. For spawning, the minimum requirement has 2 purposes: (1) avoid spawning too many neurons given the same amount of maturity, i.e. avoid DoS (2) the resulting neuron should always have >= 1 ICP stake (minimum stake) with worst maturity modulation (-5%). For maturity disbursement, (2) isn't needed anymore, and the 1/0.95 value is more confusing than 1, without a good reason.

What

Check the maturity disbursement >= 1 ICP, directly, without applying worst maturity modulation.

Note that since we are lowering the minimum requirement, all maturity disbursement requests that previously succeed will still succeed, while some requests ([1, 1 / 0.95)) that previously fail will now succeed. This should not cause confusing behavior in the frontends, and thus frontend changes can be released independently from this.

[github-actions]

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