chore(*): add mathlib4 synchronization comments (#18485)
Regenerated from the [port status wiki page](https://github.com/leanprover-community/mathlib/wiki/mathlib4-port-status).
Relates to the following files:
* `category_theory.adjunction.fully_faithful`
* `category_theory.adjunction.whiskering`
* `category_theory.category.Cat`
* `category_theory.category.galois_connection`
* `category_theory.fin_category`
* `category_theory.isomorphism_classes`
* `category_theory.lifting_properties.adjunction`
* `category_theory.lifting_properties.basic`
* `category_theory.limits.shapes.strong_epi`
* `category_theory.skeletal`
* `combinatorics.additive.pluennecke_ruzsa`
* `data.qpf.multivariate.constructions.sigma`
* `field_theory.subfield`
* `group_theory.order_of_element`
* `linear_algebra.projection`
* `set_theory.ordinal.principal`
* `topology.algebra.order.group`
* `topology.continuous_function.ordered`
Author
github-actions[bot]
