Build app with play services 8.4.0

I am using OneSignal push notification plugin and in my android SDK manager google play services version is 31.
So the app is building with google play services 9.2.0 but many of my clients have version 8.4 or 8.7 in their devices
I need to build my app with an older version like 8.4.0
I changed the above line in platforms/android/ :

and I have created build-extras.gradle and add this lines:
> dependencies {

        compile ""

but nothing changed and apk is still built with version 9.2.0.