rabbitmq-server: set erlang version

pkgs/top-level/all-packages.nix

···
   rabbitmq-server = callPackage ../servers/amqp/rabbitmq-server {
     inherit (darwin.apple_sdk.frameworks) AppKit Carbon Cocoa;
     elixir = beam_nox.interpreters.elixir_1_8;
-    erlang = erlang_nox;
+    erlang = beam_nox.interpreters.erlangR23;
   };
 
   radicale1 = callPackage ../servers/radicale/1.x.nix { };