chore(*): add mathlib4 synchronization comments (#18832)
Regenerated from the [port status wiki page](https://github.com/leanprover-community/mathlib/wiki/mathlib4-port-status).
Relates to the following files:
* `algebra.homology.exact`
* `algebra.homology.flip`
* `algebra.homology.functor`
* `algebra.homology.homology`
* `algebra.homology.single`
* `category_theory.monad.types`
* `category_theory.subobject.types`
* `computability.tm_computable`
* `control.bitraversable.lemmas`
* `data.qpf.univariate.basic`
* `data.real.cardinality`
* `model_theory.encoding`
* `ring_theory.localization.ideal`
* `topology.algebra.valuation`
* `topology.metric_space.cantor_scheme`
* `topology.urysohns_lemma`
