Req Adapter: Task max timeout fixed at 5 sec

[tuomohopia]

Req adapter timeout fixed

at 5 seconds

When using Req adapter, requests seem to be capped at 5 seconds in terms of timeouts. Because that's the default that gets passed to Task.await/2 here:

reverse_proxy_plug/lib/reverse_proxy_plug/http_client/adapters/req.ex

Line 103 in 420e97a

|> Task.await()

.

The default comes from https://hexdocs.pm/elixir/1.17.3/Task.html#await/2.

[stocks29]

It would be great to get this fixed by merging the PR from @mwhitworth

I put up another PR which I believe is a simpler fix: #239