Remove property for task with undefined behavior (Collatz.yml)

[MartinSpiessl]

This task contains an overflow, so stating the termination property makes no sense, especially since no verdict is given.

[PhilippWendler]

A case of #480.

[MartinSpiessl]

#480 is related, but Collatz.yml is the only one I found in my experiments with the SV-COMP21 results that has the property without an expected verdict, so I would like to at least fix this such that there is no task without expected verdict in SV-COMP.

#480 is about tasks that have other properties (with expected verdict).

[dbeyer]

I like the suggestion to add a new task with a bound. Would you be willing to add it @peterschrammel ? (in another pull request?)