chore(*): add mathlib4 synchronization comments (#19181)
Regenerated from the [port status wiki page](https://github.com/leanprover-community/mathlib/wiki/mathlib4-port-status).
Relates to the following files:
* `algebra.category.Module.simple`
* `algebra.category.Module.subobject`
* `algebra.lie.engel`
* `analysis.normed_space.star.continuous_functional_calculus`
* `category_theory.bicategory.functor_bicategory`
* `category_theory.groupoid.subgroupoid`
* `category_theory.monoidal.center`
* `linear_algebra.eigenspace.minpoly`
* `measure_theory.integral.torus_integral`
* `probability.density`
* `topology.metric_space.hausdorff_dimension`
