cvc5 is too fast for challenge problem in timeout test

[arjunvish]

The challenge problem used to test solver timeouts is solved too quickly by cvc5:

CVC5
      Test itself is valid and completes (0.4 s):  OK (0.41s)
      Test runs past timeout:                      IGNORED
        solver runs test faster than reasonable timing threshold; skipping
      Test with goal timeout (0.25 s):             OK (0.42s)

We'll need to come up with a new challenge problem that takes cvc5 at least a couple of seconds longer (and is also challenging for the other solvers)