chore(*): add mathlib4 synchronization comments (#18897)
Regenerated from the [port status wiki page](https://github.com/leanprover-community/mathlib/wiki/mathlib4-port-status).
Relates to the following files:
* `algebra.category.Group.Z_Module_equivalence`
* `algebraic_topology.extra_degeneracy`
* `category_theory.abelian.exact`
* `category_theory.abelian.transfer`
* `category_theory.monad.coequalizer`
* `category_theory.preadditive.projective_resolution`
* `data.mv_polynomial.polynomial`
* `data.ordmap.ordnode`
* `field_theory.tower`
* `linear_algebra.projective_space.basic`
* `linear_algebra.projective_space.independence`
* `linear_algebra.symplectic_group`
* `topology.category.Profinite.basic`
* `topology.category.Profinite.projective`
