_prob undefined in Scenario3_q2.jl

[zterner-mitre]

The variable _prob is undefined in Scenario3_q2.jl. We are trying to compare the MSEs computed in these two sections. The text says that the SIRHD model had a lower MSE, so it is clear that _prob should not be edited to _prob2, but it is unclear if _prob was defined somewhere previously and deleted, or where that variable originated.