fix(http): make Hackney use HTTP/1.1 only

Hackney 4 negotiates HTTP/2 and shares one connection per host. The
media proxy closes a response with :hackney.close/1, which stops the
whole connection, so parallel downloads from one host broke each other.

config/config.exs

@@ -163,6 +163,10 @@ config :mime, :types, %{
 
 config :tesla, adapter: Tesla.Adapter.Hackney
 
+# Hackney 4 shares one HTTP/2 connection per host, and closing one response
+# (as the media proxy does) stops it for every other stream on it.
+config :hackney, default_protocols: [:http1]
+
 # Configures http settings, upstream proxy etc.
 config :pleroma, :http,
   proxy_url: nil,