Remove redundant insufficient balance action. (#2994)
Remove redundant insufficient balance action. (#2994)

`RUNACCOUNTMIXER_INSUFFICIENT_BALANCE` is not longer dispatched so it can be removed. Also removes a redundant i18n string so it wont be translated unnecessarily.
decred/decrediton,decred/decrediton,decred/decrediton,decred/decrediton,decred/decrediton,decred/decrediton