Suggested changes to build.common.gradle

[alan412]

• Remove ndkVersion This isn't needed and creates difficulty with CI pipelines. Without it, it uses the NDK that goes along with the SDK that has been downloaded instead of timing to a single one.
• Remove "arm64-v8a" from ndk under buildTypes. (This is required for using EasyOpenCV. And since we don't need ARM64, why make life harder for beginner teams?)