duplicate txn error does not consider step being moved

[dbeal-eth]

suppose you have cannonfile like

[invoke.one]
step =1
[invoke.two]
step = 2

and change it to

[invoke.one]
step = 2
[invoke.two]
step = 2

if you have already built it, you will get an error that the txn has already been run. but in reality, the txn has been removed from a previous step and moved to a new step.

this will likely be fixed by topological cannonfiles.