Do not force resolution to IPV4 addresses

[pakrym-stripe]

Stripe does not have an AAAA record so it's impossible to resolve an IPv6 address for api.stripe.com.

Forcing resolution to IPv4 via CURL_IPRESOLVE_V4 interferes with IPv4 over IPv6 proxy network setups and DNS64.

We also don't enforce the same setting in any of the other libraries.

Changelog

• Do not force resolution to IPv4 - Forcing IPv4 was causing hard-to-understand failures for users in IPv6-only environments. If you want to force IPv4 yourself, you can do so by telling the API client to use a CurlClient other than the default

$curl = new \Stripe\HttpClient\CurlClient([CURLOPT_IPRESOLVE => CURL_IPRESOLVE_V4]);
\Stripe\ApiRequestor::setHttpClient($curl);

[richardm-stripe]

LGTM. Let's write a careful ## Changelog in the PR description so that if any users begin suffering from #1045, they can find the workaround and we can investigate.

[pakrym-stripe]

We'll wait until the next major to merge this.

[ramya-stripe]

@pakrym-stripe, @richardm-stripe, Reviving this PR with the base as the next-major branch. This is stiil a go?

[pakrym-stripe]

@ramya-stripe , yes, but needs a changelog entry as @richardm-stripe mentioned.