Revert "Convert maintainer file entries to attributes, add github handles"

This reverts commit aa47bac04f.

maintainers/scripts/check-maintainer-github-handles.sh

@@ -1,23 +0,0 @@
-#!/usr/bin/env nix-shell
-#!nix-shell -i bash -p jq parallel
-
-# Example how to work with the `lib.maintainers` attrset.
-# Can be used to check whether all user handles are still valid.
-
-set -e
-
-# checks whether a user handle can be found on github
-function checkUser {
-    local user="$1"
-    local status=
-    status="$(curl --silent --head "https://github.com/${user}" | grep Status)"
-    printf "%s\t\t\t\t%s\n" "$status" "$user"
-}
-export -f checkUser
-
-# output the maintainers set as json
-# and filter out the github username of each maintainer (if it exists)
-# then check 100 at the same time
-nix-instantiate -A lib.maintainers --eval --strict --json \
-    | jq -r '.[]|.github' \
-    | parallel -j100 checkUser