ruby: remove unsupported versions (#34927)

* remove EOL ruby versions for security and maintenance reasons.
* only expose ruby_MAJOR_MINOR to the top-level. we don't provide
guarantees for the TINY version.
* mark all related packages as broken
* switch the default ruby version from 2.3.x to 2.4.x

pkgs/applications/editors/vim/macvim.nix

@@ -103,6 +103,7 @@ stdenv.mkDerivation rec {
   '';
 
   meta = with stdenv.lib; {
+    broken = true; # needs ruby 2.2
     description = "Vim - the text editor - for macOS";
     homepage    = https://github.com/b4winckler/macvim;
     license = licenses.vim;