chore: forward-port leanprover-community/mathlib#18687 (#3202)

This change was already applied in a previous forward-port in order to fix compilation. The porting note can now be removed, since mathlib3 now contains the same generalization.

* [`algebra.star.self_adjoint`@`9abfa6f0727d5adc99067e325e15d1a9de17fd8e`..`a6ece35404f60597c651689c1b46ead86de5ac1b`](https://leanprover-community.github.io/mathlib-port-status/file/algebra/star/self_adjoint?range=9abfa6f0727d5adc99067e325e15d1a9de17fd8e..a6ece35404f60597c651689c1b46ead86de5ac1b)

Mathlib/Algebra/Star/SelfAdjoint.lean

@@ -4,7 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Frédéric Dupuis
 
 ! This file was ported from Lean 3 source module algebra.star.self_adjoint
-! leanprover-community/mathlib commit 9abfa6f0727d5adc99067e325e15d1a9de17fd8e
+! leanprover-community/mathlib commit a6ece35404f60597c651689c1b46ead86de5ac1b
 ! Please do not edit these lines, except to modify the commit id
 ! if you have ported upstream changes.
 -/
@@ -252,7 +252,6 @@ end DivisionRing
 
 section Semifield
 
--- porting note: generalize to `Semifield` to fix lean4#2074-related errors
 variable [Semifield R] [StarRing R]
 
 theorem div {x y : R} (hx : IsSelfAdjoint x) (hy : IsSelfAdjoint y) : IsSelfAdjoint (x / y) := by