Don't run warnings in a task.

lib/pleroma/application.ex

@@ -22,7 +22,7 @@ defmodule Pleroma.Application do
   def start(_type, _args) do
     import Cachex.Spec
 
-    Task.start(&Pleroma.DeprecationWarnings.warn/0)
+    Pleroma.DeprecationWarnings.warn()
 
     # Define workers and child supervisors to be supervised
     children =