hackney adapter helper: enable TLSv1.3

The list of TLS versions was added by 8bd2b6eb when hackney version was pinned to 1.15.2. Later hackney version was upgraded (166455c8) but the list of TLS versions wasn't removed. From the hackney point of view, this list has been replaced by the OTP defaults since 0.16.0 (734694ea4e24f267864c459a2f050e943adc6694).

It looks like the same issue already occurred before: 0cb7b0ea.

A way to test this issue (where example.com is an ActivityPub site which uses TLSv1.3 only):

$ PLEROMA_CONFIG_PATH=/path/to/config.exs pleroma start_iex
Erlang/OTP 22 [erts-10.7.2.16] [source] [64-bit] [smp:2:2] [ds:2:2:10] [async-threads:1] [hipe]

Erlang/OTP 22 [erts-10.7.2.16] [source] [64-bit] [smp:2:2] [ds:2:2:10] [async-threads:1] [hipe]

Interactive Elixir (1.10.4) - press Ctrl+C to exit (type h() ENTER for help)
iex(pleroma@127.0.0.1)2> Pleroma.Object.Fetcher.fetch_and_contain_remote_object_from_id("https://example.com/@/Nick/")
{:error,
 {:tls_alert,
  {:protocol_version,
   'TLS client: In state hello received SERVER ALERT: Fatal - Protocol Version\n'}}}

With this patch, the output is the expected one.

iex(pleroma@127.0.0.1)3> Pleroma.Object.Fetcher.fetch_and_contain_remote_object_from_id("https://example.com/@/Nick/")
{:error,
{:ok,
 %{
   "@context" => [
     "https://www.w3.org/ns/activitystreams",
     "https://w3id.org/security/v1",
     %{
       "Emoji" => "toot:Emoji",
       "Hashtag" => "as:Hashtag",
       "atomUri" => "ostatus:atomUri",
       "conversation" => "ostatus:conversation",
       "featured" => "toot:featured",
       "focalPoint" => %{"@container" => "@list", "@id" => "toot:focalPoint"},
       "inReplyToAtomUri" => "ostatus:inReplyToAtomUri",
       "manuallyApprovesFollowers" => "as:manuallyApprovesFollowers",
       "movedTo" => "as:movedTo",
       "ostatus" => "http://ostatus.org#",
       "sensitive" => "as:sensitive",
       "toot" => "http://joinmastodon.org/ns#"
     }
   ],
   "endpoints" => %{"sharedInbox" => "https://example.com/inbox"},
   "followers" => "https://example.com/@/Nick/followers",
   "following" => nil,
   "icon" => %{
     "type" => "Image",
     "url" => "https://example.com/static/media/[...].png"
   },
   "id" => "https://example.com/@/Nick/",
   "inbox" => "https://example.com/@/Nick/inbox",
   "liked" => nil,
   "name" => "Nick",
   "outbox" => "https://example.com/@/Nick/outbox",
   "preferredUsername" => "Nick",
   "publicKey" => %{
     "id" => "https://example.com/@/Nick/#main-key",
     "owner" => "https://example.com/@/Nick/",
     "publicKeyPem" => "[...]
   },
   "summary" => "",
   "type" => "Person",
   "url" => "https://example.com/@/Nick/"
 }}