chore(*): add mathlib4 synchronization comments (#18992)
Regenerated from the [port status wiki page](https://github.com/leanprover-community/mathlib/wiki/mathlib4-port-status).
Relates to the following files:
* `algebra.module.injective`
* `category_theory.preadditive.yoneda.injective`
* `category_theory.preadditive.yoneda.projective`
* `category_theory.sites.cover_lifting`
* `category_theory.sites.pushforward`
* `computability.reduce`
* `computability.tm_to_partrec`
* `measure_theory.group.measurable_equiv`
* `measure_theory.group.pointwise`
* `probability.cond_count`
* `probability.probability_mass_function.monad`
* `topology.continuous_function.polynomial`
