Let's just remove CA predicate locks and be done with it

This is what we should have done in #369742: CA predicates maybe don't need to be prevented from being evaluated more than once. from the beginning, I think. Every so often I run into a problem that's caused by predicates being run more than once on a page load, but so far I've managed to find a workaround. Frankly, I'm tired of having to do that every time, so this patch removes that mechanism completely.