remove fricklerhandwerk from CODEOWNERS

stepping aside as a Nix maintainer:
https://discourse.nixos.org/t/time-to-step-aside/61050

Author: fricklerhandwerk

.github/CODEOWNERS

@@ -11,16 +11,7 @@
 .github/CODEOWNERS @edolstra
 
 # Documentation of built-in functions
-src/libexpr/primops.cc @roberth @fricklerhandwerk
-
-# Documentation of settings
-src/libexpr/eval-settings.hh @fricklerhandwerk
-src/libstore/globals.hh @fricklerhandwerk
-
-# Documentation
-doc/manual @fricklerhandwerk
-maintainers/*.md @fricklerhandwerk
-src/**/*.md @fricklerhandwerk
+src/libexpr/primops.cc @roberth
 
 # Libstore layer
 /src/libstore @ericson2314