NyaaSpam: Fix bug when `mins` >= 60
NyaaSpam: Fix bug when `mins` >= 60

Trying to be clever almost never pays off and it once again shows. Here
I tried to calculate the projected DueTime in one step, but that will
not work the the DateTimeOffset constructor - which does not accept a
value larger than 59 for minutes.

IvionSauce/MeidoBot