treewide: remove unused with statements from maintainer lists

$ find -type f -name '*.nix' -print0 | xargs -P "$(nproc)" -0 sed -i \
  -e 's!with lib.maintainers; \[ *\];![ ];!' \
  -e 's!with maintainers; \[ *\];![ ];!'

pkgs/development/libraries/git2-cpp/default.nix

@@ -23,7 +23,7 @@ stdenv.mkDerivation (finalAttrs: {
     homepage = "https://github.com/ken-matsui/git2-cpp";
     description = "libgit2 bindings for C++";
     license = licenses.mit;
-    maintainers = with maintainers; [ ];
+    maintainers = [ ];
     platforms = platforms.unix;
   };
 })