nixpkgs-core: remove wolfgangwalther (#1939)

See NixOS/org#229

Author: wolfgangwalther

core/src/content/teams/030_nixpkgs-core.mdx

@@ -6,8 +6,6 @@ members:
     github: alyssais
   - name: emilazy
     github: emilazy
-  - name: wolfgangwalther
-    github: wolfgangwalther
 contact:
   - name: Discourse
     href: https://discourse.nixos.org/g/nixpkgs-core