Downgrade Plug to 1.10.x, revert upload_limit tuple to function change

This should fix setting the upload limit in the database as found in:
https://queer.hacktivis.me/notice/A8XUZp74Cg7eYNEMxU

This reverts commit 7d350b73f5.

mix.exs

@@ -199,6 +199,9 @@ defmodule Pleroma.Mixfile do
       {:eblurhash, "~> 1.1.0"},
       {:open_api_spex, "~> 3.10"},
 
+      # indirect dependency version override
+      {:plug, "~> 1.10.4", override: true},
+
       ## dev & test
       {:ex_doc, "~> 0.22", only: :dev, runtime: false},
       {:ex_machina, "~> 2.4", only: :test},