fix(http): drop the partial body from truncated-read errors

Hackney 4.9 returns {:error, {:closed, partial}}. RelMe caches errors,
so it would keep up to max_body bytes per URL.

test/pleroma/http_test.exs

@@ -29,6 +29,10 @@ defmodule Pleroma.HTTPTest do
       %{method: :post, url: "http://example.com/world"} ->
         %Tesla.Env{status: 200, body: "world"}
 
+      # Hackney 4.9 hands back the bytes it read before the peer closed.
+      %{method: :get, url: "http://example.com/truncated"} ->
+        {:error, {:closed, "partial body"}}
+
       %{method: :get, url: "https://example.com/emoji/Pack%201/koronebless.png?foo=bar+baz"} ->
         %Tesla.Env{status: 200, body: "emoji data"}
 
@@ -81,6 +85,12 @@ defmodule Pleroma.HTTPTest do
     end
   end
 
+  describe "get/1 with a truncated body" do
+    test "drops the partial body from the error" do
+      assert HTTP.get("http://example.com/truncated") == {:error, :closed}
+    end
+  end
+
   describe "get/2 (with headers)" do
     test "returns successfully result for json content-type" do
       assert HTTP.get("http://example.com/hello", [{"content-type", "application/json"}]) ==