Revert "Upgrade Elixir to 1.6.6 (#2653)"

This reverts commit d3a9fbf62f1e505371a55629485d6c64e973733c.
rebar2 (which is still used) is not able to cope with this change
it should check lib/elixir/src/elixir.app.src instead of src/elixir.app.src
as src/elixir.app.src moved away, currently check fails and this breaks
jenkins tests.

options: use rebar3, or drop rebar completely to rely only on mix.

1 files changed, 1 insertions, 1 deletions

diff --git a/mix.exs b/mix.exs
index 8f13482f0..2e136884d 100644
--- a/mix.exs
+++ b/mix.exs
@@ -5,7 +5,7 @@ defmodule Ejabberd.Mixfile do
     [app: :ejabberd,
      version: "18.9.0",
      description: description(),
-     elixir: "~> 1.6",
+     elixir: "~> 1.4",
      elixirc_paths: ["lib"],
      compile_path: ".",
      compilers: [:asn1] ++ Mix.compilers,