pub/url_launcher/android/src/main/AndroidManifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
  package="io.flutter.plugins.urllauncher"
  android:versionCode="1"
  android:versionName="0.0.1">

  <uses-sdk android:minSdkVersion="16" android:targetSdkVersion="21" />
</manifest>