fix: remove unnecessary unitTests.returnDefaultValues from android/build.gradle

Verified the new A0Auth0ModuleNetworkingOptionsTest suite passes identically
with or without this option — nothing in buildNetworkingClient()'s path
touches an unstubbed Android framework API, so the fallback is dead config.

Author: NandanPrabhu

android/build.gradle

@@ -51,10 +51,6 @@ android {
     abortOnError false
   }
 
-  testOptions {
-    unitTests.returnDefaultValues = true
-  }
-
   compileOptions {
     sourceCompatibility JavaVersion.VERSION_17
     targetCompatibility JavaVersion.VERSION_17