chore(*): add mathlib4 synchronization comments (#19231)
Regenerated from the [port status wiki page](https://github.com/leanprover-community/mathlib/wiki/mathlib4-port-status).
Relates to the following files:
* `algebra.big_operators.norm_num`
* `algebraic_geometry.projective_spectrum.scheme`
* `analysis.analytic.inverse`
* `analysis.inner_product_space.of_norm`
* `analysis.normed.group.SemiNormedGroup.completion`
* `category_theory.monad.monadicity`
* `data.buffer.parser.basic`
* `data.buffer.parser.numeral`
* `data.fintype.array`
* `data.hash_map`
* `geometry.manifold.algebra.left_invariant_derivation`
* `geometry.manifold.cont_mdiff_mfderiv`
* `geometry.manifold.vector_bundle.hom`
* `linear_algebra.clifford_algebra.even_equiv`
* `ring_theory.etale`
* `ring_theory.kaehler`
* `tactic.group`
* `testing.slim_check.functions`
