Bump OkHttp to v4

[exoego]

Why ?

OkHttp v3 series no longer get maintenance.
The last version v3.14.9 was published in about 3 years ago (2020-05-17).

https://github.com/square/okhttp
These platforms lack support for TLS 1.2 and should not be used. But because upgrading is difficult, we will backport critical fixes to the 3.12.x branch through December 31, 2021.

Is it safe to bump to v4?

It is safe since we shade OkHttp dependencies.

In addition to that, OkHttp v4 offers:

https://square.github.io/okhttp/changelogs/upgrading_to_okhttp_4/
Binary compatibility is the ability to compile a program against OkHttp 3.x, and then to run it against OkHttp 4.x. We’re using the excellent japicmp library via its Gradle plugin to enforce binary compatibility.
Java source compatibility is the ability to upgrade Java uses of OkHttp 3.x to 4.x without changing .java files.

[exoego]

Closing since v4 has kotlin dependency