Fix EventSourcingIntro sample

[rud]

Output was inconsistent before, so want that to be fixed.

[jeremydmiller]

@rud Thanks for doing this, but where in the world is this code? I'll have to admit I didn't even know it was there

[rud]

It's part of the samples in src/samples/EventSourcingIntro, to my untrained eyes it seemed like a great first example to try and run locally. Hope I didn't spoil the puzzle for others :D

[rud]

Ooh, now that I have you @jeremydmiller, would the TreatWarningsAsErrors setting be something that might be useful to enable elsewhere in the project?

In this particular case it absolutely pinpointed the bug, maybe there are other similar cases elsewhere that could be uncovered with gradually rolling it out?

[jeremydmiller]

@rud If you'd asked me that yesterday, I'd have said I don't have time for that noise -- but then a bug got into Wolverine that Rider was trying to flag. So, maybe?