Updating the Android target template.

[dawlane]

As jcenter is soon to be biting the dust. I would recommend that the build.gradle file be updated to read:

buildscript {
    repositories {
        google()
        mavenCentral()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:${ANDROID_GRADLE_VERSION}'
    }
}

allprojects {
    tasks.withType(JavaCompile) {
        options.compilerArgs << "-Xlint:-deprecation" << "-Xlint:-unchecked"
    }
    repositories {
        google()
        mavenCentral()
        jcenter()
${ANDROID_REPOSITORIES}
    }
}

After the date that was announced for the final repository shutdown (1 Feb 2022). jcenter should be removed.

I've also noticed that the modules/native/androidgame.java has a some mistakes with the overrides of:
onStart, onRestart and onStop. They call the wrong overridden super members.