android: keep okio classes

Fixes running profile builds.

android/app/proguard-rules.pro

 -keep class sun.misc.Unsafe { *; }
 -dontwarn java.nio.file.*
 -dontwarn org.codehaus.mojo.animal_sniffer.IgnoreJRERequirement
+-keep class okio.** { *; }
 -dontwarn okio.**
 
 # WebRTC