QueryCombinationIter should not implement ExactSizeIterator

[nicopap]

Bevy version

QueryCombinationIter can very easily have a length greater than usize::MAX, therefore shouldn't implement ExactSizeIterator.

Know length iterators with potential greater-than-usize::MAX length in std::iter and itertools do not implement ExactSizeIterator, because the value of len cannot be accurate if the length exceeds usize. (iter::Repeat, iter::Intersperse, itertools::Product, itertools::Combinations do not implement ExactSizeIterator)

[ottah]

I've implemented this fix in #5895. I'm new to rust/bevy so any help with improving the PR will be appreciated!