Update expectation for Exercise 8

[Tiefseetauchner]

Hi!

According to the expected output "Aufgabe 8", we should expect the following:

Enter CommissionClass: 2
Your Commission Rate was set to 0.02
Enter CommissionClass: 100
Your Commission Rate was set to 0.00

However, the expectation in the second case was 0.0. This PR fixes that unfortunate plunder.

Best, Lena