Update CODEOWNERS (#1280) (#1282)

After reviewing the members of the `qiskit-nature` Github organization
team, the only member without explicit other permissions in this repo
was @stefan-woerner. Based on an offline discussion he agreed that his
ownership and permissions are no longer required which is why I am
removing him from this file. Subsequently, I will also remove the
`qiskit-nature` team from the repository settings since we can rather
add individual members in the future (rather than first adding everyone
to the qiskit-community Github organization and subsequently a single
team; since we will have less overlapping members across multiple
repositories).

(cherry picked from commit aec7d3d)

# Conflicts:
#	.github/CODEOWNERS

Co-authored-by: Max Rossmannek <[email protected]>

.github/CODEOWNERS

@@ -15,11 +15,11 @@
 # review/merging of PRs in different subsections of the repository.
 
 # Global rule, unless specialized by a later one
-* @stefan-woerner @woodsp-ibm @mrossinek @robertodr @matteoacrossi
+* @woodsp-ibm @mrossinek @robertodr @matteoacrossi
 
 # Qiskit Nature modules
-mappers/  @stefan-woerner @woodsp-ibm @mrossinek @robertodr @matteoacrossi @ftroisi
-operators/  @stefan-woerner @woodsp-ibm @mrossinek @robertodr @matteoacrossi @ftroisi
+mappers/  @woodsp-ibm @mrossinek @robertodr @matteoacrossi @ftroisi
+operators/  @woodsp-ibm @mrossinek @robertodr @matteoacrossi @ftroisi
 
 # Override the release notes directories to have _no_ code owners, so any review
 # from somebody with write access is acceptable.