Stop failing if object is disposed twice.

[polina-c]

The failures affect running application.

This fix will unblock the PR: flutter/flutter#131998

[kenzieschmoll]

Instead of allowing objects to be disposed twice, shouldn't we prevent them from being disposed twice?

[polina-c]

Instead of allowing objects to be disposed twice, shouldn't we prevent them from being disposed twice?

It may be good idea, but for future scope of leak_tracker. Right now it is not leak tracker responsibility.
But, if we decide to add it to scope, failure is not right way to handle double disposal, because leak_tracker should not change the application or test behaviour.

So, if we want to handle it, it requires additional discussion and design.
Right now i want to turn off failures to stop blocking big PR in flutter that may get merge conflicts.

Created TODO and issue for discussion: #118

[jacob314]