fix: remove rejected events system source (#3012)

Co-authored-by: Adam Mokan <amokan@gmail.com>

Author: Ziinc

lib/logflare/sources/source.ex

@@ -107,7 +107,7 @@ defmodule Logflare.Sources.Source do
     end
   end
 
-  @system_source_types [:rejected_events, :metrics, :logs]
+  @system_source_types [:metrics, :logs]
 
   typed_schema "sources" do
     field :name, :string

test/logflare/users/users_test.exs

@@ -127,7 +127,6 @@ defmodule Logflare.UsersTest do
 
       assert Enum.any?(system_sources, &(&1.system_source_type == :metrics))
       assert Enum.any?(system_sources, &(&1.system_source_type == :logs))
-      assert Enum.any?(system_sources, &(&1.system_source_type == :rejected_events))
 
       assert Users.Cache.get(user.id).system_monitoring