relax elixir requirement

since we no longer build on 1.11 we don't have to watch out for elixir-lang/elixir#11110

apps/elixir_ls_debugger/mix.exs

@@ -9,7 +9,7 @@ defmodule ElixirLS.Debugger.Mixfile do
       config_path: "../../config/config.exs",
       deps_path: "../../deps",
       lockfile: "../../mix.lock",
-      elixir: ">= 1.12.3",
+      elixir: ">= 1.12.0",
       build_embedded: false,
       start_permanent: true,
       build_per_environment: false,

apps/elixir_ls_utils/lib/minimum_version.ex

@@ -11,7 +11,7 @@ defmodule ElixirLS.Utils.MinimumVersion do
   end
 
   def check_elixir_version do
-    if Version.match?(System.version(), ">= 1.12.3") do
+    if Version.match?(System.version(), ">= 1.12.0") do
       otp_release = String.to_integer(System.otp_release())
 
       if Version.match?(System.version(), "< 1.13.0") and otp_release == 24 do
@@ -23,7 +23,7 @@ defmodule ElixirLS.Utils.MinimumVersion do
       end
     else
       {:error,
-       "Elixir versions below 1.12.3 are not supported. (Currently running v#{System.version()})"}
+       "Elixir versions below 1.12.0 are not supported. (Currently running v#{System.version()})"}
     end
   end
 end

apps/elixir_ls_utils/mix.exs

@@ -10,7 +10,7 @@ defmodule ElixirLS.Utils.Mixfile do
       deps_path: "../../deps",
       elixirc_paths: elixirc_paths(Mix.env()),
       lockfile: "../../mix.lock",
-      elixir: ">= 1.12.3",
+      elixir: ">= 1.12.0",
       build_embedded: false,
       start_permanent: false,
       build_per_environment: false,

apps/language_server/mix.exs

@@ -5,7 +5,7 @@ defmodule ElixirLS.LanguageServer.Mixfile do
     [
       app: :language_server,
       version: "0.12.0",
-      elixir: ">= 1.12.3",
+      elixir: ">= 1.12.0",
       build_path: "../../_build",
       config_path: "../../config/config.exs",
       deps_path: "../../deps",

mix.exs

@@ -9,7 +9,7 @@ defmodule ElixirLS.Mixfile do
       start_permanent: Mix.env() == :prod,
       build_per_environment: false,
       deps: deps(),
-      elixir: ">= 1.12.3",
+      elixir: ">= 1.12.0",
       dialyzer: [
         plt_add_apps: [:dialyxir_vendored, :debugger, :dialyzer, :ex_unit],
         flags: [