Revert to use OkHttp as fallback engine

This partially reverts commit 7b67210876

Reason for revert: `setApplicationProtocols` used by Apache 5 HC is not
available until API 29.

README.md

@@ -75,7 +75,7 @@ and [Dynamic Color](https://m3.material.io/styles/color/dynamic-color/overview)
 
 \* Archives and GIFs are not supported
 
-** Fall back to Apache5 on devices that don't support [HttpEngine](https://developer.android.com/reference/android/net/http/HttpEngine)
+** Fall back to OkHttp on devices that don't support [HttpEngine](https://developer.android.com/reference/android/net/http/HttpEngine)
 
 <a href="https://github.com/FooIbar/EhViewer/releases">
 <img alt="Get it on GitHub" src="https://github.com/Ehviewer-Overhauled/Art/blob/master/get-it-on-github.svg" width="200px"/>
@@ -95,6 +95,7 @@ Here is the libraries
 - [Kotlin & KotlinX](https://kotlinlang.org/)
 - [MDC-Android](https://github.com/material-components/material-components-android)
 - [Material Icons](https://github.com/google/material-design-icons)
+- [OkHttp](https://square.github.io/okhttp/)
 - [Ktor](https://ktor.io/)
 - [Coil](https://coil-kt.github.io/coil/)
 - [Compose Destinations](https://composedestinations.rafaelcosta.xyz/)