feat: support Elixir 1.14.4+ (#294)

1.14.4 was the first Elixir release to support OTP 26:
https://github.com/elixir-lang/elixir/releases/tag/v1.14.4

There doesn't appear to be anything about Oidcc which requires features
in 1.15, so Oidcc can express support for slightly earlier versions.

.github/workflows/part_test.yml

@@ -170,6 +170,8 @@ jobs:
       fail-fast: false
       matrix:
         include:
+          - elixir: "1.14.5"
+            unstable: false
           - elixir: "1.15.0"
             unstable: false
           - elixir: "1.15.7"

mix.exs

@@ -8,7 +8,7 @@ defmodule Oidcc.Mixfile do
     [
       app: :oidcc,
       version: to_string(@props[:vsn]),
-      elixir: "~> 1.15",
+      elixir: ">= 1.14.4 and < 2.0.0",
       erlc_options: erlc_options(Mix.env()),
       build_embedded: Mix.env() == :prod,
       start_permanent: Mix.env() == :prod,