Objective checking code allows exploiting park value+repay loan goals

[Gymnasiast]

Because the objective calculation does not update the park value before checking, it is possible to just demolish a bunch of rides, repay the loan and have the objective complete before the park value is calculated again.

This should be changed to recalculate the park value before checking the objective. In case this is not feasible (it might cost too much performance to calculate it every day), it should at least recalculate when it looks like the objective has been completed.

Example: https://www.youtube.com/watch?v=V2mscAQFSF0