cosmetic: replace deprecated Tuple.append

Everytime a tuple is append a new one is allocated and all data copied
over. Keeping it a list until all entries are converted avoids this.

lib/pleroma/config_db.ex

@@ -303,7 +303,9 @@ def to_elixir_types(%{"tuple" => [":partial_chain", entity]}) do
   end
 
   def to_elixir_types(%{"tuple" => entity}) do
-    Enum.reduce(entity, {}, &Tuple.append(&2, to_elixir_types(&1)))
+    entity
+    |> Enum.map(&to_elixir_types(&1))
+    |> List.to_tuple()
   end
 
   def to_elixir_types(entity) when is_map(entity) do