Fix mix task pleroma.instance dialyzer error

lib/mix/tasks/pleroma/instance.ex:356:pattern_match_cov
The pattern
:variable_

can never match, because previous clauses completely cover the type
%{
  :anonymize => boolean(),
  :dedupe => boolean(),
  :read_description => boolean(),
  :strip_location => boolean()
}.

lib/mix/tasks/pleroma/instance.ex

@@ -352,6 +352,4 @@ defmodule Mix.Tasks.Pleroma.Instance do
 
     enabled_filters
   end
-
-  defp upload_filters(_), do: []
 end