Enable :logger_backends application on < Elixir 1.15

mix.exs

@@ -73,14 +73,15 @@ defmodule Pleroma.Mixfile do
   def application do
     [
       mod: {Pleroma.Application, []},
-      extra_applications: [
+      extra_applications:
+        [
           :logger,
           :runtime_tools,
           :comeonin,
           :fast_sanitize,
           :os_mon,
           :ssl
-      ],
+        ] ++ logger_application(),
       included_applications: [:ex_syslogger]
     ]
   end
@@ -109,6 +110,14 @@ defmodule Pleroma.Mixfile do
     for s <- oauth_strategy_packages, do: {String.to_atom(s), ">= 0.0.0"}
   end
 
+  defp logger_application do
+    if Version.match?(System.version(), "<1.15.0-rc.0") do
+      []
+    else
+      [:logger_backends]
+    end
+  end
+
   defp logger_deps do
     if Version.match?(System.version(), "<1.15.0-rc.0") do
       []